STAT 245 Lecture Notes - Lecture 8: Statistical Hypothesis Testing, Confidence Interval, Test Statistic
Stat 244 – Exercises #8
Solutions
PROBLEM A: Stopping distances on dry pavement when travelling at 90 kph for a random sample of 12
vehicles equipped with a certain all-season tire were measured in metres and recorded as follows.
37 43 30 38 49 52 48 45 37 40 47 53
It is assumed that the population of vehicle stopping distances is Normally distributed.
1. Using the above sample information, determine a 99% confidence interval for the true mean
stopping distance on dry pavement with this all-season tire and travelling at 90 kph. Give your
answer correct to two places of decimal.
The confidence interval for is
The above data yields , and .
Given
The confidence interval for is
2. A government agency was concerned that the mean stopping distance of these tires on dry
pavement and travelling at 90 kph might exceed 40 metres. Perform the appropriate statistical
test to test this claim at the 5% level of significance. Give the complete 8-step procedure.
1. Hypotheses: vs.
2. Significance Level:
3. Test Statistic:
4. Calculate TS:
