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Refer back to the pizza-delivery Try It exercise. The population standard deviation is six minutes and the sample mean delivery time is $36$minutes. Use a sample size of $20$. Find a$95$% confidence interval estimate for the true mean pizza delivery time

State the estimated distribution of $P′.$Construct a $92\%$Confidence Interval for the true proportion of girls in the ages $8to12$beginning ice-skating classes at the Ice Chalet.

How much area is in both tails (combined)?

Suppose we know that a confidence interval is ($42.12,47.88$). Find the error bound and the sample mean.

The data in Table 8.10 are the result of a random survey of 39 national flags (with replacement between picks) from various countries. We are interested in finding a confidence interval for the true mean number of colors on a national flag. Let X = the number of colors on a national flag.

Construct a 95% confidence interval for the true mean number of colors on national flags.

Using the same $\stackrel{¯}{x}$ , $s_x$ , and n = 39, how would the error bound change if the confidence level were reduced to 90%? Why?

The population standard deviation for the height of high school basketball players is three inches. If we want to be $95$% confident that the sample mean height is within one inch of the true population mean height, how many randomly selected students must be surveyed?

Of 1,050 randomly selected adults, 360 identified themselves as manual laborers, 280 identified themselves as non-manual wage earners, 250 identified themselves as midlevel managers, and 160 identified themselves as executives. In the survey, 82% of manual laborers preferred trucks, 62% of non-manual wage earners preferred trucks, 54% of mid-level managers preferred trucks, and 26% of executives preferred trucks

Construct a 95% confidence interval. State the confidence interval, sketch the graph, and calculate the error bound

Of 1,050 randomly selected adults, 360 identified themselves as manual laborers, 280 identified themselves as non-manual wage earners, 250 identified themselves as midlevel managers, and 160 identified themselves as executives. In the survey, 82% of manual laborers preferred trucks, 62% of non-manual wage earners preferred trucks, 54% of mid-level managers preferred trucks, and 26% of executives preferred trucks.

Suppose we want to lower the sampling error. What is one way to accomplish that?

A poll of 1,200 voters asked what the most significant issue was in the upcoming election. Sixty-five percent answered the economy. We are interested in the population proportion of voters who feel the economy is the most important.

Define the random variable X in words

A poll of 1,200 voters asked what the most significant issue was in the upcoming election. Sixty-five percent answered the economy. We are interested in the population proportion of voters who feel the economy is the most important.

Define the random variable P′ in words.