Proportions or Means Inference

What is the z* value for a 88%confidence interval?

• 1.175

• 1.555

• 1.645

• 1.96

Which of the following is true pertaining to a 2-proportion z-interval?

• There are no restrictions on sample size 

• This interval can be found even if the samples are not random

• The population should be large, relative to each of the sample sizes

• So long as all conditions are met for one sample, you do not need to check conditions for the other sample

What additional condition must be checked for a 2-proportion test or interval compared to a 1-proportion test or interval?

• You must make sure that the samples are random

• You must make sure that the two samples are independent from one another

• You must make sure that the sum of the samples' sizes are smaller than 10% of the whole population

• The conditions are exactly the same

In a past General Social Survey, a random sample of men and women answered the question “Are you a member of any sports clubs?” Based on the sample data, 95% confidence intervals for the population proportion who would answer “yes” are .13 to .19 for women and .247 to .33 for men. Based on these results, you can reasonably conclude that 

• At least 25% of American men and American women belong to sports clubs.

• At least 16% of American women belong to sports clubs. 

• There is a difference between the proportions of American men and American women who belong to sports clubs.

• There is no conclusive evidence of a gender difference in the proportion belonging to sports clubs

A test was conducted to see if there was evidence that more than 10% of the population is left-handed. Ho: p = 0.10, Ha: p >0.10. A p-value of 1.10 is found. What can we conclude?

• There is not evidence that more than 10% of people are left-handed

• We can conclude that more than 10% of people are left-handed

• There is evidence that more than 10% of people are left-handed

• The person who ran this test made an error

Which of the following is not a condition that needs to be checked for inference for proportions?

• Ensuring that the sample is independent

• Making sure the sample is representative of the population

• n*p₀ > 10, n*q₀ > 10

• n*p-hat > 10, n*q-hat > 10

z* is the critical value for which of the following tests/intervals?

I. 1-prop. z-test

II. 2-prop. z-interval

III. 1-sample t-test

IV. 2-sample t-interval

• I only

• I and II only

• I, II, and III only

• All of the above

• III and IV only

Which calculator function allows you to find the test statistic for a 2-proportion z-interval?

• normalcdf

• invNorm

• tcdf

• invT

What is the critical value for a 95% confidence interval for proportions?

• z = 1.645

• z = 1.96

• z = -1.645

• z = -1.96

84% of Russians believe that the Sochi Olympics promoted sports development in Russia. The poll of 2,000 people had a margin of error of 2%. What is the best description of what this 2% M.E. means?

• Not all of the 2,000 adults knew something about the Olympics

• About 2% of the 2,000 adults polled refused to answer

• About 2% of adults were expected to change their minds between the time of the poll and its publication time

• The difference between the sample percentage and the population percentage is likely to be less than 2%

• There is a 2% chance that this survey captured the true proportion of Russian adult citizens who would answer yes to the question.