Using Statcrunch or the t-table report the t-critical that you multiply by the s
ID: 3153566 • Letter: U
Question
Using Statcrunch or the t-table report the t-critical that you multiply by the standard error to form the margin of error for a:
99% confidence interval for a mean with 7 observations.
95% confidence interval for a mean with 19 observations.
90% confidence interval for a mean with 1001 observations.
What happens to the t-critical values as the degrees of freedom?
A study on binge drinking among college students reported a 95% confidence interval for the proportion of students who consume more than five drinks a week as (0.45, 0.53).
What is the margin of error for this study?
What is the standard error of the sample proportion?
What was the estimated sample proportion?
How large was the sample?
State how the following will affect the margin of error, the standard error and the confidence interval.
Increasing the sample size.
Decreasing the sample size.
Increasing the confidence level.
Explanation / Answer
Using Statcrunch or the t-table report the t-critical that you multiply by the standard error to form the margin of error for a:
99% confidence interval for a mean with 7 observations.
Df=6, t= 3.707
95% confidence interval for a mean with 19 observations.
Df=18, t=2.101
90% confidence interval for a mean with 1001 observations.
Df=1000, t=1.646
What happens to the t-critical values as the degrees of freedom?
When degrees of freedom increases, t critical values decreases.
A study on binge drinking among college students reported a 95% confidence interval for the proportion of students who consume more than five drinks a week as (0.45, 0.53).
What is the margin of error for this study? (0.53-0.45)/2= 0.04
What is the standard error of the sample proportion? 0.04/1.96 = 0.0204
What was the estimated sample proportion? (0.53+0.45)/2 = p=0.49
How large was the sample?
se=sqrt(p(1-p)/n))
n=(0.49*0.51) /0.02042 = 600.4
sample size =600
State how the following will affect the margin of error, the standard error and the confidence interval.
Increasing the sample size.
margin of error will decrease, the standard error will decrease and the confidence interval will decrease
Decreasing the sample size.
margin of error will increase, the standard error will increase and the confidence interval will increase
Increasing the confidence level.
margin of error will increase, the standard error will remain same and the confidence interval will increase
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