Chronic respiratory diseases are a group of chronic diseases affecting the airways and other structures of the lungs. Common chronic respiratory diseases as included in ICD-10 are Asthma, Bronchiectasis, Chronic Obstructive Lung Disease including chronic obstructive pulmonary disease (COPD), bronchitis and emphysema, chronic rhinosinusitis, hypersensitivity pneumonitis, Lung Cancer, Lung fibrosis etc. (WHO, 2003). Chronic respiratory diseases account for 4% of the global and 8.3% of the overall burden of chronic diseases, having a major adverse impact on sufferers’ quality of life (QoL), disability, and productivity, and resulting in increased economic burden for both the individual and community (WHO, 2007).
COPD is the third leading cause of combined morbidity and mortality (WHO, 2014). More than 3 million people died of COPD in 2012, which is equal to 6% of all deaths globally that year (WHO, 2015). The prevalence of COPD in India is 3.67% (Jindal, S.K et al, 2012). Crude estimates suggest there are 30 million COPD patients in India (Salvi et al,2012).
Chronic Obstructive Pulmonary Disease (COPD), a common preventable and treatable disease, is characterized by persistent airflow limitation that is usually progressive and associated with an enhanced chronic inflammatory response in the airways and the lung to noxious particles or gases. Exacerbations and comorbidities contribute to the overall severity in individual patients. (Global Strategy of Diagnosis, Management and Prevention of COPD, 2016).
COPD is progressive in nature. It is marked by difficulty in breathing that may be due to cigarette smoking and long term exposure to other lung irritants such as air pollution, thereby negatively affecting the lungs. Increased breathlessness when active, persistent cough with phlegm and frequent chest infections are key features of COPD. It is a disease of airway obstruction. It may be due to obstruction of small airways (obstructive bronchiolitis) or parenchymal destruction (emphysema).
A clinical diagnosis of COPD should be considered in any patient who has dyspnea, chronic cough or sputum production, and a history of exposure to risk factors for the disease.
Spirometry is required to make the diagnosis; the presence of a post-bronchodilator FEV1/FVC < 0.70 confirms the presence of persistent airflow limitation and thus of COPD.
Smoking is the greatest risk factor for the development of COPD. It is estimated that 80-90% of the risk for COPD can be accounted for by tobacco smoke (American Thoracic Society, 1995). Air pollution is an irritant for exacerbations of COPD. Air pollutants include smoke, particulate matter, acid rain, reactive gases and ozone. The negative effects of these airborne pollutants can be damaging to the structure and functional capabilities of the lung. There exists a hereditary predisposition for COPD. As early as the 1800s, hereditary factors were implicated in the onset of COPD, especially emphysema (Sherrill et al., 1990)
COPD often coexists with other diseases (comorbidities) that may have a significant impact on prognosis According to Global Initiative for Chronic Obstructive Lung Disease (GOLD) (2016), COPD is comorbid with Depression and Anxiety, Impaired cognitive functioning, Cardiovascular disease, Osteoporosis, Lung cancer, Metabolic syndrome and diabetes and Bronchiectasis.
Illness Perception
One of the psychological factors that is considered important in this context is illness perception (Weldam, 2014). Illness perceptions are the organized cognitive representations or beliefs that patients have about their illness. These perceptions have been found to be important determinants of behaviour and have been associated with a number of important outcomes, such as treatment adherence and functional recovery.
Illness perceptions are idiosyncratic representations of symptoms and illness, formed on the basis of personal and observed encounters with illness as well as information from medical sources (e.g., physicians and books) and from the “popular†media, friends, parents, the Internet, and fellow patients. Whether they are medically accurate, these representations critically shape the responses (coping behaviors) of patients and consequently, their outcome.
Illness perceptions are the central concept of the Common Sense Model (CSM) (Leventhal, et al, 2003). Leventhal, et al. (1984) identified five dimensions within the cognitive representation of illness:
i. identity—the label the person uses to describe the illness and the symptoms they view as being part of the disease;
ii. consequences—the expected effects and outcome of the illness;
iii. cause— personal ideas about the cause of the illness;
iv. timeline— how long the patient believes the illness will last;
v. cure or control—the extent to which the patient believes that they can recover from or control the illness.
The perception of illness affects the way patients cope with their complaints and is important for outcome (Petrie KJ, et al, 2007; Philip EJ et al, 2009). Researchers have indicated that illness perceptions affect coping, functional adaptation and are tied to fear and distress.
Beliefs about disease are created during the whole life and can significantly influence the course of the disease and the treatment’s effect. Knowledge about disease and its acceptance are also changing with duration of the illness (Dyduch A, et al, 2008).
Metacognition
Flavell (1979) proposed the term Metacognition. Metacognition means any kind of knowledge or cognitive processes in which there is assessment, monitoring and cognitive control (Lips et al.,2002). It includes cognitive processes as well as experiences and cognitive regulation. Metacognitive knowledge refers to the acquisition of knowledge about cognitive processes and knowledge on how to use cognitive control processes. Metacognition theory emphasizes on beliefs and knowledge that individuals have about their own thinking patterns. Metacognitions are the positive and negative beliefs about thinking.
The study of metacognitions is mainly associated with the self-regulatory executive function (S-REF) model developed by Wells and Matthews (1996). According to the S-REF model, metacognitions predispose individuals to develop response patterns to perceived behavioral, cognitive, or emotional difficulties that are characterized by heightened self-focused attention, avoidance, recyclical thinking patterns, threat monitoring, and thought suppression. Configurations of these strategies constitute a cognitive–attentional syndrome (CAS) (Wells, 2000). Activation of the CAS is problematic because it causes negative thoughts and emotions to persist, it fails to modify dysfunctional self-beliefs, and it increases the accessibility of negative information (Wells, 2000). Metacognitions have been divided into two broad sets of beliefs in the S-REF model (Wells, 2008) : (1) negative beliefs concerning the significance, controllability, and danger of particular types of thoughts (e.g., “it is bad to think thought X†or “I need to control thought Xâ€) and (2) positive beliefs about coping strategies that impact on mental states (such as “worrying will help me get things sorted out in my mind†or “brooding will help me solve the problemâ€).
The construct of metacognitions differs from that of illness perceptions because it also embodies beliefs about cognitive, attentional, and behavioural responses (such as ruminating and worry about symptoms, self focussed attention, and avoidance) to symptoms (Kollman et al, 2016).
Rationale of the study
COPD is the third leading cause of combined morbidity and mortality. Literature suggests importance of Metacognition in Chronic Illnesses like CHD, Cancer, Chronic Pain, Chronic Fatigue Syndrome. But it has not been studied in COPD. Hence, Metacognition is being studied in COPD. The relationship between Illness Perception and Metacognition will help in understanding holistic response to COPD illness and management of the patient. Further effect of depressive and anxiety symptoms are evident in chronic illnesses. The role of depression and anxiety on metacognitions and illness perception in COPD patients is yet to be studied.
Aims and Objectives
• To study Illness Perception and Metacognition in Chronic Obstructive Pulmonary Disease (COPD) patients and their relationship, if any.
• To study the relationship between depressive symptoms & Illness Perception and Metacognition in patients of COPD.
• To study the relationship between anxiety symptoms & Illness Perception and Metacognition in patients of COPD.
The aim of the study is to explore the illness perception and metacognitive beliefs in patients with chronic obstructive pulmonary disease. The secondary aims of the study were to study the relationship between anxiety and illness perception and metacognitions. Also, to study the relationship between depression and illness perception and metacognition.
Epidemiology of COPD
A systematic review on prevalence of COPD in India was done by McKay et al (2012) in order to understand sustainable management strategies in India. The study indicated paucity of data availability and thus need to systematically study the prevalence of COPD in India. Only four studies were identified that estimated prevalences between 6.5% and 7.7%.
Jindal SK (2012) is his article mentions about the variability of prevalence of COPD. Western countries report a higher prevalence rate than the Asian countries. A combined prevalence of 6.3 % has been pointed out in 12-Asia Pacific countries. There is variation in the methodology of surveys that have taken place in India. In men, 2 to 22 percent and in women 1.2 to 19 percent prevalence rates have been indicated, although these results are based on unvalidated questionnaires and interviews. Indian study of Epidemiology of Asthma, Respiratory symptoms and Chronic bronchitis (INSEARCH) included four centres- Chandigarh, Delhi, Kanpur and Bangalore reported overall prevalence rates of 5% in men and 3.2 in women over 35 years of age.
Studies of Anxiety and Depression in COPD patients
A recent study on prevalence of psychiatric comorbidity in COPD patients was undertaken by Chaudhry SC et al (2016). The aim was to study the frequency of psychiatric comorbidity in COPD patients and their relation with the severity of COPD. The study comprised of 74 COPD patients and 74 controls whose psychiatric comorbidity was assessed using Mini International Neuropsychiatric Interview. The study found that 28.4% COPD had psychiatric comorbidity.8.1% of the cases had clinically significant depression and 9.5% had anxiety disorders. Also, the findings indicate that the psychiatric comorbidity rise with the increase in the severity of COPD.
Negi H, et al (2014) studied the presence of depression and its risk factors in patients with COPD using Patient Health Questionnaire-9 (PHQ-9). The study indicated that about one-fifth of the patients with COPD had severe symptoms of depression.
A systematic review and meta-analysis on bidirectional associations between clinically relevant depression or anxiety and COPD by Evan Atlantis, et al (2013) concluded that depression and anxiety adversely affect prognosis in COPD. It can also increase the risk of exacerbation. Also, COPD can increase the risk of developing depression.
In another study, on mental disorders in COPD (Vogele & Leupodt, 2007) demonstrate high prevalence of anxiety in COPD patients and that this may be mediated cognitive processes.
Studies on Illness Perception in COPD
Tiemensma J., Gaab E., et al (2016) conducted a study on Illness Perception and coping determine quality of life in COPD patients. The study aimed to examine the association between illness perception, coping and quality of life in COPD patients. The sample comprised of 100 COPD patients. The tools used were Brief Illness Perception Questionnaire (B-IPQ), Utrecht Proactive Coping Competence (UPCC) and a QOL item. The study found that patients with better understanding of COPD utilized more proactive coping strategies. A more intense emotional response to COPD was related to less proactive coping. More proactive coping techniques also reported to have better QOL. Patients reported more strongly affected illness perceptions compared to people with a cold and patients with asthma.
Another study titled Illness Perceptions predict exercise capacity and psychological well being after pulmonary rehabilitation in COPD patients by Zoeckler N, et al in 2014 aimed at exploring if illness perceptions had an influence on exercise capacity and quality of life pointed out that perceptions about their own illness held by patients of COPD has an effect on exercise capacity and quality of life. The study comprised a sample of 96 COPD patients. The tool used in the study were Illness Perception Questionnaire- Revised (IPQ-R), Health Related Quality of life, depression and COPD specific anxiety questionnaire
Weldam S et al (2014) conducted a cross-sectional study to analyze the degree to which the specific dimensions of illness perceptions contribute to health related quality of life in COPD patients. The findings of the study indicate the association between illness perception and HRQoL of COPD patients. Also, it indicated that HRQoL is associated with severity of dyspnoea as experienced by the patient.
A study on Illness Perception and Quality of Life in Patients with Chronic Obstructive Pulmonary Disease by Scarloo et al. (2007) was undertaken with the objective of identifying cognitive and emotional representations that contribute to improvement of health and quality of life. The tools used were Illness Perception Questionnaire (IPQ-R), RAND SF-36 Health Survey (SF-36), Quality of Life for Respiratory Illness Questionnaire (QoLRIQ). It was suggested that patients who had a reduced attention to the symptoms, with more positive beliefs about the effects and outcomes of their illness, and with less strong emotional reactions to the illness, had higher QoL scores.
Hence, role of illness perception is important in medical illnesses like COPD.
Studies on Metacognition in Chronic Illness
Cook & Salmon et al (2015) researched on the association of metacognitive beliefs with emotional distress after diagnosis of cancer. The study comprised of 229 patients with cancer. The tools used were Hospital anxiety and Depression scale, Impact of Events scale, Illness Perception Questionnaire- Revised, Metacognition Questionnaire-30, Penn State Worry Questionnaire and Cognitive Attentional Syndrome Scale (CAS-I). The findings of the research indicate that the negative cognitions activate CAS thereby causing and maintaining distress. Also, emotional distress may be a maladaptive metacognition.
Metacognition was also studied in Parkinson’s disease by Brown R.G. (2014) in the study titled ‘Metacognitions, anxiety and distress related to motor fluctuation in Parkinson’s disease’. The study was done on 106 patients with Parkinson’s Disease using Hospital Depression and Anxiety Scale, Movement Disorder Society revision of the unified Parkinson’s disease rating scale, Addenbrooke’s Cognitive examination-revised, the intolerance of uncertainty scale and Metacognitions Questionnaire-30. The study indicated that anxiety was significantly related metacognitive factors when controlling of motor experiences. The off-period distress was significantly related to metacognitions concerning uncontrollability and danger.
Yoshida et al (2012) in the study titled ‘Cognitions, Metacognitions and Chronic Pain’ used the tools Thought Control Questionnaire (TCQ), Pain catastrophizing scale (PCS) and Survey of Pain Attitudes (SOPA) Control Scale on 129 patients with chronic pain. The study found that pain control beliefs and catastrophizing are associated with metacognitions. Role of maintenance of pain related cognitive content is mediated by metacognitions.
In another study on ‘Metacognitions and negative emotions as predictors of symptom severity in Chronic Fatigue Syndrome’ by L.Maher-Edwards et al (2011) suggest that positive emotions are negatively correlated with measures of symptom severity. Metacognitions and measures of symptom severity were positively correlated. Also, symptom severity was better predicted by metacognitions than anxiety and depression.
Metacogntive beliefs have also been studied in people with multiple sclerosis by Zand N.K. et al (2013). The study was taken place in Iranian M.S center which included 90 patients with MS and 90 healthy subjects. Significant differences were found in negative meta-cogntive beliefs and cognition efficacy. The study also indicated that as negative meta cognitive beliefs increased, there is a reduction in life expectancy and 26.1% variance was found in life expectancy due to cognitive beliefs.
Hence, the study is being undertaken to analyze if illness perception is effected by anxiety or depression in Chronic Obstructive Pulmonary Disease. Also, if metacognitions are effected due to anxiety or depression in Chronic Obstructive Pulmonary Disease. Additionally, it has also been studied if metacognitions and illness perception effect each other in COPD.
Design Method
The study is a cross-sectional study.
Sampling Technique
Purposive sampling method was used for sample selection.
Research Sample
The study sample includes registered patients of COPD attending Respiratory Medicine OPD, KGMU, Lucknow on specified days. The sample constitutes patients diagnosed with COPD by consultant in charge. The sample in the study comprises of 45 COPD patients.
Inclusion Criteria
1. Patients consulting primarily for COPD, as diagnosed by Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines*.
2. Age 40 years to 69 years
Exclusion Criteria
1. Patients not giving written informed consent for the study.
2. Patients with a psychiatric disorder except for Depressive Disorder, Anxiety Disorders and Mental and Behavioral Disorders due to use of tobacco.
3. Patients who are symptomatic and/or have unstable comorbid medical illness.
4. Acute exacerbations of COPD symptoms
Tools
1. Written Informed Consent Form
2. Sociodemographic Performa
3. Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines.
4. ICD-10-DCR
5. Mini International Neuropsychiatric Interview (M.I.N.I.) v.6.0.0 [Sheehan DV, Lecrubier Y, 2006]
6. Beck Depression Inventory- Hindi Version (Beck, 1961)
7. Penn State Worry Questionnaire (Meyer, Miller, Metzger & Borkovec,1990)
8. Illness Perception Questionnaire- Revised (Moss-Morris et al.,2002)
9. Metacognition Questionnaire-30 (MCQ-30) (Wells & Cartweight-Hatton, 2004)
Description of the tools:
Informed consent form
Informed consent was designed to obtain written informed consent from cases prior to their inclusion in the study.
Semi Structured Performa
Semi structured performa was designed specifically to record the socio-demographic details and clinical variables. Clinical variables include duration of illness, spirometry findings, past history, family history, personal history, medical history, mental status examination and diagnosis.
Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines
GOLD program in their report Global Strategy for the diagnosis, management and prevention of COPD summarize the current state of COPD. It is a strategy document for health care professionals to use as a tool to implement effective management programs. It draws together a measure of the impact of the patient’s symptoms and an assessment of the patient’s risk of having serious adverse health event in future.
ICD-10 DCR
The International statistical classification of Diseases and related health problems 10th Revision (ICD-10) is a coding system of diseases and signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or diseases, as classified by the World Health Organization (WHO, 1993). The Diagnostic Criteria for Research accompanying the ICD-10 (DCR) are designed for use in research. Their content is derived from the Glossary to the chapter on Mental and behavioral disorders in the ICD-10, Chapter V (F). they provide specific criteria for diagnosis contained in the “Clinical Descriptions and Diagnostic Guidelines†that have been produced for general clinical and educational use by the psychiatrist and other mental health professionals (WHO, 1992).
MINI International Neuropsychiatric Interview (M.I.N.I. 6.0)
The MINI International Neuropsychiatric Interview (M.I.N.I 6.0) is a short, structured diagnostic interview developed by Sheehan et al (1998). MINI provides diagnoses according to DSM-IV and ICD-10 criteria psychiatric disorders. MINI used by psychiatrists, clinicians and other health professionals with an administration time of approximately 15 minutes. The MINI contains 19 modules that evaluate 17 Axis I disorders (e.g Major Depressive Disorder, OCD, GAD etc). MINI has high level of inter-rater reliability with all k values above 0.75 (a cut off described by Fleiss as indicating excellent agreement. The value range from 0.79 (current mania) to 1.00 (Major Depressive Disorder, OCD, current alcohol dependence, anorexia).
Beck Depression Inventory-Hindi version
The Beck Depression Inventory is a 21-question multiple-choice self-report inventory. It is one of the most widely used instruments for measuring the severity of depression. In its current version the questionnaire is designed for individuals aged 13 and over, and is composed of items relating to symptoms of depression such as hopelessness and irritability, cognitions such as guilt or feelings of being punished, as well as physical symptoms such as fatigue, weight loss, and lack of interest in sex. Internal consistency for the BDI ranges from .73 to .92 with a mean of .86. (Beck, Steer, & Garbin, 1988). A split-half reliability of 0.86 was given in addition to yielding alpha coefficients ranging from 0.76 to 0.95 in psychiatric samples. Content validity would seem to be quite high since the BDI appears to evaluate a wide variety of symptoms and attitudes associated with depression. Coefficients of .65 and .67 were obtained in comparing results of the BDI with psychiatric ratings of patients.
Penn State Worry Questionnaire (PSWQ)
Meyer et al. (1990) designed to measure the trait of worry. It was created to evaluate the tendency of an individual to worry, the excessiveness or intensity of worry and tendency for worrying to be generalized and not restricted to one or a small number of situations. It is a 16 item self report questionnaire rated on likert scale from 1 to 5 (1= not at all typical to 5= very typical. items 1, 3, 8, 10 and 11 are reverse scored. Total score of items range from 16-80. High degree of internal consistency is found in diverse population (clinical as well as non-clinical). Test-retest reliability ranged from 0.75 over 2 week interval to 0.92 over 8 to 10 week interval. it shows a good convergence with the other measures of worry in non clinical and student population.
Illness Perception Questionnaire- Revised (IPQ-R)
IPQ-R was developed by Moss-Morris et al. (2002). it is used to assess illness perceptions. The subscales of the IPQ-R are timeline acute/ chronic, timeline cyclical, consequences, personal control, treatment control, identity, illness coherence, emotional representations and cause. With the exception of the identity subscale, responses are rated on a 5-point scale. Scores on the identity subscale are the sum of symptoms attributed to illness. High scores on the identity, timeline, consequences, and cyclical dimensions represent strongly held beliefs about the number of symptoms attributed to the illness, the chronicity of the condition, the negative consequences of the illness, and the cyclical nature of the condition. High scores on the personal control, treatment control and coherence dimensions represent positive beliefs about the controllability of the illness and a personal understanding of the condition. The IPQ-R has been used with a wide variety of patient groups. It has good reliability and validity and is successful in predicting different aspects of adaptation and recovery in chronic illness (Moss-Morris et al. 2002).
Metacognition Questionnaire -30 (MCQ-30)
MCQ-30 was designed by Wells & Cartwright-Hatton (2004). It assesses key components of the metacognitive model of emotional disorder. It is concerned with the beliefs people have about their thinking. MCQ-30 is a short version of the original MCQ and assesses individual differences in the five factors that are metacognitive beliefs, judgments and monitoring tendencies. It consists of 30 items that are rated on 4 point Likert scale. The questionnaire comprises if five subscales:
Factor 1: Positive beliefs about worry (positive beliefs), which assess the extent to which the person believes that worrying is helpful (e.g worrying helps me to cope).
Factor 2: Negative beliefs about worry concerning uncontrollability of thoughts and danger, which measures the extent to which a person believes that worrying is uncontrollable and dangerous (e.g. when I start worrying I cannot stop).
Factor 3: Beliefs about cognitive confidence measures confidence in memory (e.g. My memory can mislead me at times).
Factor 4: Beliefs about the need to control thoughts (e.g. not being able to control my thoughts is a sign of weakness).
Factor 5: Cognitive self consciousness, which assesses the tendency to monitor one’s own thoughts and focus on one’s thinking processes (e.g. I pay close attention to the way my mind works)
Subscale scores range from 6 to 24, and total scores range from 30 to 120, with higher scores indicating higher levels of unhelpful metacognitions.
MCQ-30 showed good internal consistency and convergent validity and acceptable to good test-retest reliability. the psychometric properties of MCQ-30 suggest that the instrument is a valuable addition to the assessment of metacognition and has an advantage of being more economical to use.
Procedure
The study was approved by Ethics Committee of the university. Patients attending the Respiratory Medicine OPD, KGMU on specified days, diagnosed with Chronic Obstructive Pulmonary Disease (COPD) by the consultant in charge on the basis of GOLD guidelines were screened as per selection criteria. Patients who were willing to give written informed consent and fulfilling the selection criteria were included in the study. Their socio-demographic details were recorded on the semi-structured Performa. M.I.N.I was applied to rule out psychiatric comorbidity. BDI was administered to assess depressive symptoms. Penn State Worry Questionnaire was administered to assess severity of anxiety. Illness Perception Questionnaire-Revised was administered to assess cognitive illness representation. MCQ-30 was administered to understand metacognitive beliefs.
Data Analysis
Data was obtained and was tabulated using Microsoft Excel 2007 software. Statistical analysis was performed on SPSS version-20.
Data was summarized as means/percentages for
• Socio demographic and clinical variables
• Scores on BDI
• Scores on PSWQ
• Scores on IPQ-R (Dimensions)
• Scores on MCQ-30 (Domains)
• Pearson’s Correlation Analysis was done between depressive symptoms and illness perception and metacognition, anxiety symptoms and illness perception and metacognition and between dimensions of illness perception and metacognition.
• ANOVA followed by bonferonni post hoc test was applied to compare scores on dimensions of illness perception and domains of metacognition among the three groups based on the stage of COPD.
Data was summarized as Mean and S.D for continuous variables. For discrete variables data was expressed in percentages and frequencies. Correlational analysis was performed to see the relationship between depressive symptoms and illness perception and metacognition, between anxiety symptoms and illness perception and metacognition and between illness perception and metacognition. Additionally, Analysis of Variance (ANOVA) followed by bonferonni post hoc test was used for continuous variables.
All tests were two-tailed. Significance was considered for p<0.05 and p<0.01.
The following statistical tests were employed:
Arithmetic Mean: Mean was obtained by adding individual observations together and dividing by the total number of observation.
Standard Deviation: It is a measure of spread of data. It is denoted by σ.
Pearson’s Correlation Coefficient: Pearson’s product moment correlation coefficient is a standardized measure of strength of relationship between two variables. It can take any value -1 (as one variable changes, the other changes in the opposite direction by the same amount), through 0 (as one variable changes the other doesn’t change at all) to +1 (as one variable changes, the other changes in the same direction by the same amount). Thus, the value of ‘r’ can be either positive, zero and negative ranging from +1 to -1. It has no unit of measurement. The formula for ‘r’is:
Analysis of Variance (ANOVA): The analysis of variance or the F test permits to evaluate three or more means at one time. Variance is the measure of the dispersion or spread of a set of scores. It describes the extent to which the scores differ from each other. The one-way analysis of variance (ANOVA) is used to determine whether there are any significant differences between the means of three or more independent groups. Two sources of variation in the scores can be identified- one that reflects the effect of the treatment is called ‘between group variation’and the one that reflects the variability within the subgroups is called the ‘within groups’. An increase in the difference among the mean results is an increase in the variance of means and it is this variance that is evaluated relative to error variance. The procedure adopted for this is called analysis of variance.