PERCEIVED CONTROL (PC)

A situation specific instrument was required to measure PC in patients with

MS and this had been recommended by Phares ( 1976). The internal/external

scale devised by Rotter (1966) had been rejected as it was a broad measure

of general beliefs of PC. The MHLC developed by Wallston et al (1976),

although health related, was not directed to any particular health situation

nor did its items reflect the construct of disability. A scale was therefore

employed which had been used by other researchers interested in PC and

disabihty but adapted so that it was relevant for use in patients with MS.

The statements which made up Partridge et al's (1989) nine item scale were

adjusted so as to focus on those behefs which might be expressed by

individuals disabled with MS.

The revised scale was then circulated to ten independent judges who were

asked to rate the statements as referring to either internal or external behefs

(Table 3). The judges conq>rised five females and five males and included

clinical and non clinical staff jfiom nursing, physiotherapy and administatrve

"There seems to be a difference in the behefs that people hold about the control that they themselves have over the outcome of a particular situation. Patients who have multiple sclerosis (MS) and different kinds of disabihty have used the foUowing statements when describing how they perceive control over their symptoms of MS. Some indicated they perceived they had control. Others perceived there was a lack of personal control i.e. that their MS is controUed by chance, luck or powerful others. Please could you indiciate with an "I" those statements which imply a behef in personal control and "E" those statements which inq)ly a behef in luck, chance or powerful others. Leave blank any statements which do not seem to reflect either internal (I) or external (E) behefs of control."

There was complete agreement between the ten judges on the assignment of

the nine items as representing either internal or external behefs of perceived

control. Statements numbered 1, 3, 4, 7 and 9 represented a behef m

internal control and statements numbered 2, 5, 6 and 8 represented a lack of

behef in personal control i.e. a behef in external control.

Procedure

Ten subjects recruited to test instruments in the pilot study were given the

PC scale (Appendix 10) with the foUowing verbatim instructions:

"These are statements other patients have made about their multiple sclerosis. Please indicate the extent to which you agree or disagree with the statements by placing a tick in ONE of the five columns on the right hand side".

The five-point Likert-type scale was scored accordingly: internal items were

scored from one to five (strongly agree - strongly disagree) and the external

items from five to one (strongly agree - strongly disagree). As the scales

were scored in the direction of extemahty, the higher scores indicated a

greater behef in external control or powerfiü others. The total possible

score was 45 and the scores of the ten patients ranged from 16 to 40 with a

TABLE 3

Statements given to judges for allocation as internal (I) or external (E).

1. I don't let MS rule my life

2. There is nothing I can do about my bladder problems 3. If I arrange things so that I don't get too tired I can do most things I want to do 4. It doesn't matter how much help you get in the end it's

your own efforts

that count

5. Luck plays a large part in how I manage 6. I don't think there is much I can do to alter my symptoms

7. I am very

determined and

mostly I can manage

my bladder

synq)toms

8. The MS stops me

from doing most

things 9. I can actually control my synq)toms to a great extent No. of judges rating item as INTERNAL 10 0 10 10 0 0 10 10 No. of judges rating item as EXTERNAL 0 10 10 10 0 10 Face Validity

This appeared to be high for all the patients who agreed to complete the

Content Validity

There was evidence of the appropriateness of the items by the fact that the

nine items were all statements made by patients about their control over

their MS. Additionally these same statements were agreed by judges as

representing behefs in either internal or external control. The statements

were similar to those used in other scales and all referred to perceived

control over symptoms of MS.

Construct validity

The aim of the scale was to determine the extent to which patients beheved

in their own personal control. Those subjects who agreed with internal

items i.e. behef in personal control, disagreed with external items i.e. behef

in chance or powerful others

Internal Consistancy

The internal consistancy of the Internal and External items of the scale is

demonstrated by the results in table 4, with a significant positive relationship

between positive items and a significant negative one between dissimilar

TABLE 4.

Perceived control scores

Correlations between Internal items and Internal

mean Items 1. 0.972**** 3. 0.895*** 5. 0.862** 7. 0.901*** 9. 0.852** Correlations between external items and External

mean Items 2. 0.911**** 4. 0.900*** 6. 0.735* 8. 0.917**** * * * * _p<0.001 * * * _{p<0.002 ** p<0.005 * p<0.05}

The correlation between the internal mean and the external mean was r -

0.851. This was corrected to -0.91(p<0.001) using the Spearman Brown

prophecy formula.