1. What factor determines whether you should use a z-score or a t statistic for a hypothesis test?

2. Several factors influence the value obtained for a t statistic. Some factors affect the numerator of the t statistic and others influence the size of the estimated standard error in the denominator. For each of the following, indicate whether the factor influences the numerator or denominator of the t statistic and determine whether the effect would be to increase the value of t (farther from zero). In each case, assume that all other factors remain constant.
a. Increase the variability of the scores.
b. Increase the number of scores in the sample.
c. Increase the difference between the sample mean and the population mean.

5. A sample of n=16 scores has a mean of M=45 and SS=960.
a. Calculate the sample standard deviation (s) and the estimated standard error for the sample mean (Sm).
b. Describe what is measured by the standard deviation and what is measured by the estimated standard error.

14. The herbal supplement ginkgo biloba is advertised as producing an increase in physical strength and stamina. To test this claim, a sample of n=36 adults is obtained and each person is instructed to take the regular daily dose of the herb for a period of 30 days. At the end of the 30-day period, each person is tested on a standard treadmill task for which the average, age-adjusted score is ? =15. The individuals in the sample produce a mean score of M=16.9 with ss=1260.
a. Are these data sufficient to conclude that the herb has a statistically significant effect using a two-tailed test with â??=.05? (Assume that the herb is expected to increase scores.)
b. What decision would be made if the researcher used a one-tailed test with â??=.05? (Assume that the herb is expected to increase scores.)

The solution gives the step by step procedure for the students t test and Z test. Null hypothesis, alternative hypothesis, critical value, test statistic and P value are given with interpretations.

The history teacher at your school needs help grading a True/False test. The students' IDs andtest answers are stored in a file.
The first entry in the file contains the answers to the test form:
TFFTFFTTTTFFTFTFTFTT
Every other entry in the file is the student's ID, followed by a blank, followed by the student's respons

1. 20 problems
2. If confidence level is not given, assume 95%
3. Please show calculation using formula and using appropriate z table, student's t table, or Poisson table, etc.
See attached file for full problem description.

A student takes the GRE and scores low on it due to having a headache. The student retakes the test when he or she is feeling better two weeks later and scores higher on the test. What can be said about the reliability and validity of the test?

A paired difference experiment produced the following results
a) Determine the values of z for which the null hypothesis, m1 -m2 = 0, would be rejected in favor of the alternative hypothesis, m1 - m2 < 0. Use a = 0.10
b) Conduct the paired difference test described in part a. Draw the appropriate conclusions.
c) What assump

One professor teaches a large section, section A, of a particular class, and on the first test of the term, the test scores in section A were approximately normally distributed with a mean of 78 and a standard deviation of 6. Another professor also teaches a large section, section B, of the same class, and on the first test of t

What are the indicators for using a t-test? Create a research scenario in which it would be correct to use a t-test, including the research question, sample size, and dependent and independent variables.

PROBLEM # 3 A certain type of cable was advertised as having a breaking strength of 1000 pounds. A test of XX pieces of this cable was conducted and the mean breaking strength of this sample was XXX pounds with a sample standard deviation of XX pounds. Conduct a two-tail hypotheses test at alpha = .05 to determine if this samp

1.A machine produces 5-inch nails. A sample of 12 nails was selected and their lengths determined. The results are as follows:
4.94 4.94 5.07 4.91 4.98 5.00 4.94 5.09 5.00 4.92 5.08 5.06
Assuming that a = 0.10, test the hypothesis that the population mean is equal to 5.
?State the null and alternate hypotheses
?&

Suggest one psychological research question that could be answered by each of the following types of statistical test:
* z test
* t test for independent samples, and t test for dependent samples