1. Suppose we wish to find the required sample size to find a 90% confidence interval...

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Statistics

1. Suppose we wish to find the required sample size to find a90% confidence interval for the population proportion with thedesired margin of error. If there is no roughestimateÂ Â Â of the population proportion, what valueshould be assumed forÂ Â ?
0.90
0.10
0.50
0.05
2. An analyst takes a random sample of 25 firms in thetelecommunications industry and constructs a confidence intervalfor the mean return for the prior year. Holding all else constant,if he increased the sample size to 30 firms, how are the standarderror of the mean and the width of the confidence intervalaffected?
Standard error of the mean Width of confidence interval
A Increases Becomes wider
B Increases Becomes narrower
C Decreases Becomes wider
D Decreases Becomes narrower
1.96(10.24/6)
1.96(3.20/6)
1.645(3.20/6)
1.645(10.24/6)
3. For a given confidence level and population standarddeviation, which of the following is true in the intervalestimation of the population mean?
If the sample size is bigger, the interval is narrower.
If the population size is smaller, the interval is narrower.
If the population size is bigger, the interval is narrower.
If the sample size is smaller, the interval is narrower.

Answer & Explanation Solved by verified expert

4.1 Ratings (834 Votes)

1 The margin of error ME critical valuewhere is the sample proportion n is the sample size ie number ofsamples under considerationIf the value of is not given we assume it to be 052 The confidence interval for the mean of a population See Answer

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	Standard error of the mean	Width of confidence interval
A	Increases	Becomes wider
B	Increases	Becomes narrower
C	Decreases	Becomes wider
D	Decreases	Becomes narrower

		If the sample size is bigger, the interval is narrower.
		If the population size is smaller, the interval is narrower.
		If the population size is bigger, the interval is narrower.
		If the sample size is smaller, the interval is narrower.