A sample of 30 lap times has mean 25.3 minutes and standard deviation 1.218 minutes. Testing $H_0:\mu=25$ against $H_1:\mu>25$ , what is the value of the test statistic?

-1.35

0.25

1.35

1.65

Explanation

z = \dfrac{\bar x - \mu_0}{s/\sqrt n} = \dfrac{25.3-25}{1.218/\sqrt{30}} = \dfrac{0.3}{0.2224} \approx 1.35

. Forgetting to divide the standard deviation by

\sqrt n

gives

0.3/1.218\approx0.25

. Reversing the subtraction order gives

-1.35

. Quoting the 5% one-tailed critical value instead of the computed statistic gives

1.65

Derived from ZIMSEC Maths Paper 1, June 2007, Q10 (Statistics)

More questions from this paper

Danho has every sitting for this paper, with your progress tracked question by question, offline.