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 Central Limit Theorem the calculated mean of the ... for smaller sample sizes) to calculate Confidence Intervals ... or test hypothesis that the sample mean can be ...

... 3-6)^2)/((6-1))= 2.75681 The critical t value for 99 ... Assume that sample mean x ̅ and sample standard deviation s ... the same as those you just calculated but that ...

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

... Lower-Tail Test Lower Critical Value -1.710882067 p-Value ... Calculations Standard Error of the Mean 70 Degrees ... the null hypothesis, since the calculated value of ...

... 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. ...

...Calculating degrees of freedom for a t-test is n-1 ... df within = 13.34/6= 2.22 Now we can calculate our F value: F = mean squares between / mean squares within ...

... criteria Reject the null hypothesis, if the calculated value of t is less than the critical value of ...Sample Mean =40.6000 Sample SD S =2.7000 n =24 df =23 t...

... 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 ...

... Directions: For #1, calculate and interpret the confidence interval ... Please show your work if you calculated manually on ... Clearly the mean stress score is in the ...