# STAT 200 HW.................

**Question description**

4. Why is a 99% confidence interval wider than a 95% confidence interval?

12. A person claims to be able to predict the outcome of flipping a coin. This

person is correct 16/25 times. Compute the 95% confidence interval on the

proportion of times this person can predict coin flips correctly. What

conclusion can you draw about this test of his ability to predict the future.

15. You take a sample of 22 from a population of test scores, and the mean of your

sample is 60. (a) You know the standard deviation of the population is 10.

What is the 99% confidence interval on the population mean. (b) Now assume

that you do not know the population standard deviation, but the standard

deviation in your sample is 10. What is the 99% confidence interval on the

mean now?

100. What is meant by the term “90% confident” when constructing a confidence interval for a mean?

a. If we took repeated samples, approximately 90% of the samples would produce the same confidence interval.

b. If we took repeated samples, approximately 90% of the confidence intervals calculated from those samples would

contain the sample mean.

c. If we took repeated samples, approximately 90% of the confidence intervals calculated from those samples would

contain the true value of the population mean.

d. If we took repeated samples, the sample mean would equal the population mean in approximately 90% of the

samples.

120. An article regarding interracial dating and marriage recently appeared in the Washington Post. Of the 1,709 randomly

selected adults, 315 identified themselves as Latinos, 323 identified themselves as blacks, 254 identified themselves as

Asians, and 779 identified themselves as whites. In this survey, 86% of blacks said that they would welcome a white person

into their families. Among Asians, 77% would welcome a white person into their families, 71% would welcome a Latino,

and 66% would welcome a black person.

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