Question

**A 90 % confidence interval (a t interval) for the mean
lives (in minutes) of Kodak AA batteries is ( 370, 430 ). Assume
that this result is based on a sample of size 25 .**

**1. What is the value of the sample mean?**

**2. What is the value of the sample standard
deviation?**

**3. Construct the 99% confidence interval**

**4. If the confidence interval (373.9233 , 426.0767) is
obtained from the same sample data, what is the degree of
confidence?**

Answer #1

A 90 % confidence interval (a t interval) for the mean lives (in
minutes) of Kodak AA batteries is ( 380, 460 ). Assume that this
result is based on a sample of size 20 .
4) If the confidence interval (385.2962 ,454.7038) is obtained
from the same sample data, what is the degree of confidence?
90%
95%
88%
85%

A 90% confidence interval for the mean height of a population
is 65.7 < u < 67.3
This result is based on a sample of
size 169. Construct a 99%
confidence interval.

1) Find the critical value t (a/2) needed to construct a
confidence interval of the given level with the given sample size.
Round the answers to three decimal places
a) 98% sample size 11
critical value-
b) for level 95% and sample size 25
critical value-
c)for level 99% and sample size 14
2) a sample of size n equals 45 has a sample mean X equals 56.9
and sample standard deviation s equals 9.4.
construct a 99% confidence interval...

1,) Construct a 90% confidence interval for the population
proportion if an obtained sample of size n = 150 has x = 30
2.) Construct a 95% confidence interval for the population mean
if an obtained sample of size n = 35 has a sample mean of 18.4 with
a sample standard deviation of 4.5.

Using the T-Table, find the following values:
a) For a 90% confidence interval with a sample size of 11, tc
=
b) For a 95% confidence interval with a sample size of 20,
tc=
c) For a 99% confidence interval with a sample size of 25,
tc=

If you construct a 90% confidence interval for the population
mean instead of a 95% confidence interval and the sample size is
smaller for the 90%, but with everything else being the same, the
confidence interval would: a. remain the same b. become narrower c.
become wider d. cannot tell without further information.

A researcher is interested in finding a 90% confidence interval
for the mean number minutes students are concentrating on their
professor during a one hour statistics lecture. The study included
102 students who averaged 34.1 minutes concentrating on their
professor during the hour lecture. The standard deviation was 12.5
minutes. Round answers to 3 decimal places where possible.
a. To compute the confidence interval use a ? t
z distribution.
b. With 90% confidence the population mean minutes of
concentration is...

construct a Confidence interval for the population
mean using the information below. Confidence level: 90%, sample
size : 139, standard deviation : 17.54, mean : 106.41.

Use the standard normal distribution or the t-distribution to
construct a 99% confidence interval for the population mean.
Justify your decision. If neither distribution can be used,
explain why. Interpret the results. In a random sample of 13
mortgage institutions, the mean interest rate was 3.59% and the
standard deviation was 0.42%. Assume the interest rates are
normally distributed.
Select the correct choice below and, if necessary, fill in any
answer boxes to complete your choice.
A. The 99% confidence...

you are calculating a confidence interval for the population
mean. Find the critical value t* from the t-Distribution Critical
Values table for each of the following situations
A 95% confidence interval based on n = 12 observations.
A 99% confidence interval from a sample of two observations.
A 90% confidence interval from a sample of size 1001.
2. Suppose you conduct a hypothesis test for the following
hypotheses from a sample of n = 25 observations, and you calculate
a...

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