# Suggested answer to exercise: Normal plot for angina and pronethalol, 1

Question 1: Using SPSS, compare the numbers of attacks on the two drug treatments using the paired t test. How does the result compare with that from the sign test in Week 4, which gave P = 0.0063?

Click Analyze, Compare Means, Paired-Samples T Test. Choose variables 'Attacks while on placebo' and 'Attacks while on pronethalol'. Click OK.

You should get the following output:

Paired Samples Statistics
Mean N Std. Deviation Std. Error Mean
Pair 1 Attacks while on placebo 53.42 12 89.069 25.712
Attacks while on pronethalol 45.75 12 97.185 28.055

Paired Samples Correlations
N Correlation Sig.
Pair 1 Attacks while on
placebo & Attacks
while on pronethalol
12 .991 .000

Paired Samples Test
Paired Differences t   df   Sig. (2-tailed)
Mean Std. Deviation Std. Error Mean 95% Confidence Interval of the Difference
Lower Upper
Pair 1 Attacks while on placebo - Attacks while on pronethalol 7.667 15.108 4.361 -1.932 17.266 1.758 11 .107

The first table shows the two variables separately. The second table shows something about the relationship between the two variables, which we shall cover in Week 8. The third table shows the results of the t test and we have P = 0.107.

The P value is considerably larger than the 0.0063 for the sign test and is not significant.