Exam 7: Inferences Based on a Single Sample: Estimation With Confidence Intervals

A newspaper reported on the topics that teenagers most want to discuss with their parents. The findings, the results of a poll, showed that 46% would like more discussion about the family's financial situation, 37% would like to talk about school, and 30% would like to talk about religion. These and other percentages were based on a national sampling of 512 teenagers. Estimate the proportion of all teenagers who want more family discussions about school. Use a 90% confidence level. A) $.37 \pm .035$ B) $.37 \pm .002$ C) $.63 \pm .035$ D) $.63 \pm .002$

A marketing research company is estimating which of two soft drinks college students prefer. A random sample of 341 college students produced the following 95% confidence interval for the proportion of college students who prefer one of the colas: (.341, .451). What additional assumptions are necessary for the interval to be valid?

Find the value of $t _ { 0 } \text { such that the following statement is true: } P \left( - t _ { 0 } \leq t \leq t _ { 0 } \right) = .95 \text { where } \mathrm { df } = 15 \text {. }$

The mean systolic blood pressure for a random sample of 28 women aged 18 -24 is 112.4 mm Hg and the standard deviation is 12.8 mm Hg. Construct a 90% confidence interval for the standard deviation σ, of the systolic blood pressures of all women aged 18-24. Round to the nearest hundredth when necessary.