Determining Sample Size . In Exercises 31–38, use the given data to find the minimum sample size required to estimate a population proportion or percentage. 36. iOS Marketshare You plan to develop a new iOS social gaming app that you believe will surpass the success of Angry Birds and Facebook combined. In forecasting revenue, you need to estimate the percentage of all smartphone and tablet devices that use the iOS operating system versus Android and other operating systems. How many smartphones and tablets must be surveyed in order to be 99% confident that your estimate is in error by no more than two percentage points? a. Assume that nothing is known about the percentage of portable devices using the iOS operating system. b. Assume that a recent survey suggests that about 43% of smartphone and tablets are using the iOS operating system (based on data from NetMarketShare). c. Does the additional survey information from part (b) have much of an effect on the sample size that is required?
Determining Sample Size . In Exercises 31–38, use the given data to find the minimum sample size required to estimate a population proportion or percentage. 36. iOS Marketshare You plan to develop a new iOS social gaming app that you believe will surpass the success of Angry Birds and Facebook combined. In forecasting revenue, you need to estimate the percentage of all smartphone and tablet devices that use the iOS operating system versus Android and other operating systems. How many smartphones and tablets must be surveyed in order to be 99% confident that your estimate is in error by no more than two percentage points? a. Assume that nothing is known about the percentage of portable devices using the iOS operating system. b. Assume that a recent survey suggests that about 43% of smartphone and tablets are using the iOS operating system (based on data from NetMarketShare). c. Does the additional survey information from part (b) have much of an effect on the sample size that is required?
Solution Summary: The author explains that the number of smart phones and tablets must be surveyed is 4,145. The critical value is the average of the z-values 2.57 and 2.58.
Determining Sample Size. In Exercises 31–38, use the given data to find the minimum sample size required to estimate a population proportion or percentage.
36. iOS Marketshare You plan to develop a new iOS social gaming app that you believe will surpass the success of Angry Birds and Facebook combined. In forecasting revenue, you need to estimate the percentage of all smartphone and tablet devices that use the iOS operating system versus Android and other operating systems. How many smartphones and tablets must be surveyed in order to be 99% confident that your estimate is in error by no more than two percentage points?
a. Assume that nothing is known about the percentage of portable devices using the iOS operating system.
b. Assume that a recent survey suggests that about 43% of smartphone and tablets are using the iOS operating system (based on data from NetMarketShare).
c. Does the additional survey information from part (b) have much of an effect on the sample size that is required?
Features Features Normal distribution is characterized by two parameters, mean (µ) and standard deviation (σ). When graphed, the mean represents the center of the bell curve and the graph is perfectly symmetric about the center. The mean, median, and mode are all equal for a normal distribution. The standard deviation measures the data's spread from the center. The higher the standard deviation, the more the data is spread out and the flatter the bell curve looks. Variance is another commonly used measure of the spread of the distribution and is equal to the square of the standard deviation.
During busy political seasons, many opinion polls are conducted. In apresidential race, how do you think the participants in polls are generally selected?Discuss any issues regarding simple random, stratified, systematic, cluster, andconvenience sampling in these polls. What about other types of polls, besides political?
Please could you explain why 0.5 was added to each upper limpit of the intervals.Thanks
28. (a) Under what conditions do we say that two random variables X and Y are
independent?
(b) Demonstrate that if X and Y are independent, then it follows that E(XY) =
E(X)E(Y);
(e) Show by a counter example that the converse of (ii) is not necessarily true.
Chapter 7 Solutions
Elementary Statistics, Books A La Carte Edition (13th Edition)
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