Chapter 9 and 10

Six years ago, 11.1% of registered births were to teenage mothers. A sociologist believes that the percentage has decreased since then. (A) Determine the null and alternative hypothesis (B) Explain what it would mean to make a Type I error (C) Explain what it would mean to make a Type II error.

(A) H0: p=0.111, H1: p<0.111 (B) The sociologist rejects the hypothesis that the percentage of births to teenage 11.1%, when it is the true percentage. (C) The sociologist fails to reject the hypothesis that the percentage of births to teenage mothers is 11.1%, when the true percentage is less than 11.1%.

What is the criterion for rejecting the null hypothesis using the P-value approach? (A) - If the P-value < -zα for a left-tailed test, or - If the P-value > -zα for a right-tailed test - If the P-value < -zα/2 for a two-tailed test, then reject the null hypothesis. (B) If P-value > α, reject the null hypothesis. (C) If P-value < α, reject the null hypothesis.

(C)

If the consequences of making a Type I error are severe, would you choose the level of significance, α, to equal 0.01, 0.05, or 0.10?

0.01

Explain what a P-value is. (A) A P-value is the probability of observing a sample statistic as extreme or more extreme than the one observed under the assumption that the statement in the null hypothesis is true. (B) A P-value is the number of standard deviations that the observed proportion is from the proportion stated in the null hypothesis. (C) A P-value is the value used to designate the area α in either the left- or right-tail of the normal curve.

(A)

Explain what "statistical significance" means.

Statistical significance means that the result observed in a sample is unusual when the null hypothesis is assumed to be true.

If we reject the null hypothesis when the statement in the null hypothesis is true, we have made a Type ____ error.

Type I error.

Explain what "80% confidence" means in a 80% confidence interval.

If 100 different confidence intervals are constructed, each based on a different sample size n from the same population, then we expect 80 of the intervals to include the parameter and 20 to not include the parameter.

The _______ _______ is a statement we are trying to find evidence to support.

alternative hypothesis

A _________ _________ is the value of a statistic that estimates the value of a parameter.

point estimate