9-2 Testing μ

When σ is known The test statistic z when σ is known: 1. State Ho and HA 2. Compute z 3. Find the P value 4. Conclude based on P-value relationship to α 5. State the conclusion

When σ is unknown The test statistic t when σ is known: 1. State Ho and HA 2. Compute z 3. Find the P value 4. Conclude based on P-value relationship to α 5. State the conclusion Degrees of freedom = n-1

This is called a one-sample t-test for the mean. The residents along Triphammer Road feel that the mean speed along the road is higher than it ought to be. To get the police to patrol more frequently they want to see if their assumption is true. α=.05 This is called a one-sample t-test for the mean. (why t-test?) They have a sample of 23 car speeds, taken on 4/11/2000. 29 29 24 34 34 34 32 34 36 28 31 31 30 27 34 29 37 36 38 29 21 31 26 Graph first to see if it is “normal”… use a histogram and your calculator

1. State the hypotheses H0: μ = 30 mph; HA: μ> 30 mph 2. Check the conditions: What kind of sample is it? Convenience but likely is a representative sample 3. Find the value of the test statistic 1.17 4. Find the P-value tcdf(lower,upper,df) 5. Compare to α and make your conclusion. .127 compared to .05? As the P-value is higher than the test statistic, I fail to reject H0 and conclude that there is not enough evidence to say the average speed is too high.