Assignment - Confidence Intervals and Minimum Sample Size QUESTION 1.1

Software testers have reported their testing results of your team's latest software release. Out of a sample of 1540 tests, 117 tests resulted in a crash. Your boss wants an estimate of the true proportion of software crashes based on this information using a 95% level of confidence. Construct a confidence interval for the proportion of sessions that result in a crash.

The lower limit of the interval is_____

The upper limit of the interval is_____

QUESTION 1.2

Nice App Inc. wants to provide a special digital reward for users that spend more than $10,000 in the first year of using their new app. In order to estimate how many of the app users will qualify, they decide to perform a study. How many customers would they need to survey to estimate the proportion of users who would qualify for this reward with a 1.5% margin of error? Use a confidence level of 99%.

You will need to survey_____ users of the app.

QUESTION 1.3

Awesome Fandom Stores sale figures increase due to the sale of certain science fiction fan products on the 4^th of May each year. Awesome Fandom has recorded the sale amounts for the last 18 years and the average sales for May 4th is $76,155.47. From past studies, we know that the standard deviation is $6,220.09. Awesome Fandom wants to estimate the sales for the upcoming May 4^th. Construct a 95% confidence interval for the mean sales on May the 4^th.

The lower limit is____

The upper limit is_____

QUESTION 1.4

Knowing how quickly players accumulate resources can impact decisions about in-game micro transactions. You are part of a design team that needs to calculate the amount of gold coins obtained by player activities by a certain level in your game. From previous studies, you know the standard deviation is 7730.9 gold coins. Your boss wants you to survey players to find the average number of gold coins players can earn by that particular level. Your boss wants to use a 90% confidence level and he wants to be certain within 500 gold coins. How many players should you survey?

You will need to survey____ players.

QUESTION 1.5

Your game publishing company is looking to find out how much lower-income users spend each month on average on a game's in-app purchases so that they can make marketing decisions. You managed to collect 404 valid survey responses and calculate the mean monthly purchase amount as $5.93. From past studies of this nature, you know that the standard deviation is $1.05. Construct a 99% confidence interval to estimate the average monthly purchases of lower-income players.

The lower limit is____

The upper limit is____

QUESTION 1.6

As a manager for an advertising company, you must plan a campaign designed to advertise a new app. A recent survey suggests that 73% of adults have used similar apps. How many adults should you survey in order to be 95% confident that your estimate is within 3% of the true population proportion of adults that will use the new app?

You will need to survey____ adults.

QUESTION 1.7

A local restaurant does not accept any reservations and only focuses on walk-in customers. The owner of the restaurant wants to find out how many walk-in customers he should plan to have every day. To that end, kept records of the number of walk-in customers for the last 63 days. The average number of daily walk-in customers was 67.3 and the sample standard deviation is 7.1. Construct a 99% confidence interval for the number of customers on a given day.

The lower limit is____

The upper limit is ____

QUESTION 1.8

In a survey of 5000 people who reside in Florida, 47% were found to get the flu vaccine every year. Construct a confidence estimate for the true proportion of Floridians who get the flu vaccine every year. Use a confidence level of 95%.

The lower limit is _____

The upper limit is ______

QUESTION 1.9

A real state conglomerate in California would like to investigate home ownership in Texas as this is a market they would like to enter. How many people should this company survey in order to determine the proportion of Texans who own their own homes? In a recent poll, 68.3% of those surveyed said that they owned a home. Construct a 99% confidence interval estimate for the proportion of adults own their own home. Use a 5% margin of error.

They need to survey_____ Texans.

QUESTION 1.10

An event promoter is planning to finance a music festival for the summer. He wants to determine how much to charge people for an all-day pass. How many people should he survey if he wants to be within 3 dollars from the mean? Use a 99% confidence level. From past studies, he knows the standard deviation is $20.

The promoter needs to survey_____ people.