Description
Instructions:

Copy your answer to each question AND the R code by which you reached your answer to a document. The answers should be correctly ordered.
Problem 1 (6 pts): The text le “carseats.txt” is a data set containing sales of child car seats at di erent stores. It consists of 11 variables but we will focus on 2 variables.
Urban: Yes and No to indicate whether the store is in an urban or rural location
US: Yes and No to indicate whether the store is in the US or not
Complete the following questions:

(2 pt) Find the 90% con dence interval to estimate the population proportion of store located in urban area and interpret the con dence interval.

(2 pt) Find the 95% con dence interval to estimate the population proportion of store located in US and interpret the con dence interval.

(2 pt) Studies found that more than 60% of stores are located in the US. Perform the hypothesis test H_{0} : p = 0:6 vs. H_{a} : p > 0:6. Make your nal conclusion based on the pvalue.
Problem 2 (4 pts): The data set whiteside is available after loading the MASS package by calling library(MASS). It consists of following 3 variables.
Insul: A factor, before or after cavitywall insulation installed
Temp: The average outside temperature in degrees Celsius
Gas: The gas consumption in 1000s of cubic feet.
Complete the following questions:

(2 pt) Find the 95% con dence interval to estimate the population mean of Gas consumption and interpret the con dence interval.

(2 pt) Before cavitywall insulation installed, the average Gas consumption was 4.75. The researcher wants to prove after cavitywall insulation installed, the average Gas consumption is less than 4.75. Perform the hypothesis test H_{0} : = 4:75 vs. H_{a} : < 4:75 using observations whose Insul = After. Make your nal conclusion based on the pvalue.
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