1. A local bank needed information concerning the checking account balances of its customers. A random sample of 15 accounts was checked. The mean balance was $686.75 with a standard deviation of $256.20. Find a 98% confidence interval for the true mean. Assume that the account balances are normally distributed.

2. Find the critical t-value that corresponds to c=0.90 and n=15.

3. A survey of 100 fatal accidents showed that 35 were alcohol related. Find a point estimate for p, the population proportion of accidents that were alcohol related.

4. The grade point averages of 10 randomly selected students are listed below. Construct a 90% confidence interval for the population standard deviation. Assume the data are normally distributed.
2.0 3.2 1.8 2.9 0.9 4.0 3.3 2.9 3.6 0.8

5. A university dean is interested in determining the proportion of students who receive some sort of financial aid. Rather than examine the records for all students, the dean randomly selects 200 students and finds that 118 of them are receiving financial aid. If the dean wanted to estimate the proportion of all students receiving financial aid to within 2% with 95% reliability, how many students would need to be sampled?

Solution Summary

This solution calculates several statistics values including mean, critical t-value and sample size

... the raw measurement data presented below, calculate the t... hypothesis, since the absolute value of calculated test statistic ... t Test for Differences in Two Means. ...

... the null hypothesis, since the calculated value of ... Calculations Standard Error of the Mean 70 Degrees ... Test Calculations Area Lower Critical Value -1.71088208 ...

... is significant difference in the mean cumulative weight loss ... if the absolute value of calculated test statistic is greater than the critical value of ...

... observations at ap level of 0.01 Calculating the Statistics. ... The standard error of the mean will be estimated ... 9.24 Calculate degrees of freedom and identify the ...

... Hence the critical t-values are -2.12 ... Standard Error of the Mean 1.264911064 Z ... Intermediate Calculations Z Value -1.880793608 Calculated Sample Size 1414.9538. ...

... Reject the null hypothesis, since the calculated value of test statistic is less than the critical value. ... ยต < 8. Details Z Test of Hypothesis for the Mean. ...

... 4. What is the critical t value at the 1% level of ... 5. Assume calculated t to be +2.70, at the 0.01 ... the null hypothesis and conclude the means are different. ...

... b. Calculate the estimated standard error for the sample mean... Reject the null hypothesis, if the calculated value of ... Details. t Test for Hypothesis of the Mean. ...

... Var / N) = SQRT(1.43 / 25) = 0.24 Then calculate t = (M ... df=24 is: t* = 1.318 Since the calculated t > critical t... Ho and accept Ha that the true mean net weight ...