Question

1. Confidence Intervals

a. Isabella wants to advertise how many chocolate chips are in each Big Chip cookie at her bakery. She randomly selects a sample of 44 cookies and finds that the number of chocolate chips per cookie in the sample has a mean of 13.6 and a standard deviation of 1.4. What is the 99% confidence interval for the number of chocolate chips per cookie for Big Chip cookies? Assume the data is from a normally distributed population. Round answers to 3 decimal places where possible.

_ < u < _

b.

The body temperatures in degrees Fahrenheit of a sample of adults in one small town are:

97.8

99.7

99.6

99

97.5

98.3

98.7

Assume body temperatures of adults are normally distributed. Based on this data, find the 95% confidence interval of the mean body temperature of adults in the town. Enter your answer as an open-interval (i.e., parentheses) accurate to 3 decimal places. Assume the data is from a normally distributed population.

95% C.I. =

c. Assume that a sample is used to estimate a population mean μμ. Find the 90% confidence interval for a sample of size 68 with a mean of 63.1 and a standard deviation of 13.1. Enter your answer as an open-interval (i.e., parentheses) accurate to 3 decimal places.

90% C.I. =

d. In a survey, 22 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $39.1 and standard deviation of $2.3. Estimate how much a typical parent would spend on their child's birthday gift (use a 90% confidence level). Give your answers to 3 decimal places.

Express your answer in the format of ¯x ±  E.
$_ ±  $_

Answer 1

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