Question

1. You have developed a new assessment tool to assess the quality of life in elderly individuals.  The tool contains 7 items and each item is based on an ordinal scale of 1-4 (1: poor, 2: fair, 3: good, 4: excellent).  You have assessed 40 older adults using this new assessment tool and you would like to establish the reliability of this instrument.  The results generated by SPSS are as follows:

Reliability Statistics

Cronbach's Alpha	Cronbach's Alpha Based on Standardized Items	N of Items
.688	.705	7

Inter-Item Correlation Matrix

	item 1	item 2	item 3	item 4	item 5	item 6	item 7
item 1	1.000	.011	.061	-.240	-.173	-.248	-.213
item 2	.011	1.000	.801	.446	.442	.416	.258
item 3	.061	.801	1.000	.527	.514	.425	.311
item 4	-.240	.446	.527	1.000	.889	.432	.168
item 5	-.173	.442	.514	.889	1.000	.422	.177
item 6	-.248	.416	.425	.432	.422	1.000	.535
item 7	-.213	.258	.311	.168	.177	.535	1.000

                                                               Item-Total Statistics

	Scale Mean if Item Deleted	Scale Variance if Item Deleted	Corrected Item-Total Correlation	Squared Multiple Correlation	Cronbach's Alpha if Item Deleted
item 1	17.2250	7.307	-.184	.187	.829
item 2	17.4250	5.174	.656	.651	.621
item 3	17.3750	4.651	.732	.705	.586
item 4	17.3250	5.251	.586	.811	.635
item 5	17.3000	5.138	.599	.796	.630
item 6	17.3750	5.061	.513	.443	.648
item 7	17.4750	5.794	.314	.331	.700

1. Interpret the Cronbach’s alpha value (0.688) in the “Reliability Statistics” table (1 mark).

2. In the “Item total statistics” table, interpret/explain the number 0.829 for item 1 (highlighted) and discuss its implications .

3. Name the study design (1 mark) and describe the experimental procedures and statistical analysis (1 mark) if you are to establish the concurrent validity of this new quality of life measure using the same sample of 40 older adults.

Answer 1

1. Cronbach’s alpha value (0.688) states the internal consistency among 7 items. A Cronbach's alpha of value 0.7 or greater indicates high internal consistency. Here, 0.688 value indicate questionable internal consistency in the data or & items in the data are somewhat consistent when combined together. However, value being close to 0.7 makes it somewhat reliable.

This indicates that the instrument consisting of these 7 items will be somewhat close in predicting quality life of elderly individuals.

2. The number 0.829 for item 1 (highlighted) in table “Item total statistics” indicates that if we remove Item 1 from our set, the Cronbach's alpha will increase to 0.829 from 0.688 which is very significant due to the difference and this is help in improving internal consistency further.

This values shows good reliability and removal of item 1 from instrument will make it very close to the true predictions for quality of life of elderly.

3. It is a measure to quality of life for elderly which makes it experimental study and It is 'internal consistency' test of reliability among 7 items indicating same. Also, once this test is reliable the experimental study results can be used to make interpretation about the quality of life. Often items are correlated and hence, removal of correlated items is recommendable.

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