Question

A trial was carried out in three general practices in the UK to find out whether telephoning patients to offer them an appointment for immunization against influenza would increase immunization uptake. In this study, attending the appointment for an immunization was the outcome of interest and receiving a telephone call was the exposure. A total of 1318 patients aged 65 to 74 years were randomly assigned to two groups. Patients in one group (n = 660) received a telephone call regarding an immunization appointment. Patients in the other group (n = 658) were not called. Of the patients who received a phone call, 328 attended the appointment for immunization as did 288 of those not called.

How many times more likely were patients to attend if they had received a personal call to make an appointment than if they had not been telephoned? (calculate to one decimal point)

Answer 1

To understand this question better, lets make a table out of the given data

Exposure	Immunized	Not immunized	Percentage of people immunized
Received a call	328	660 - 328 = 332	49.7%
Not received a call	288	658 - 288 = 370	43.7%
Total	616	702	46.7%

Clearly in case of group 1(intervention group), almost 49.7% people received immunization while in case of group 2(control group) only 43.7% received immunization.

Dividing both the figures we get 49.7% / 43.7% = 1.14

Which means that patients who receive a personal call to make an appointment are 1.14 times more likely to get immunization than people who are not telephoned.