# Inferential tests

I have been struggling with these questions for days now (see file attached). Can you please help? thanks.

See attachment for full set of questions:

30. A retailer wants to obtain some current data on his customers' demographics (age, income, household size) and product preferences. He surveys all customers in his store that day. This sampling design is called:

a. simple random sampling

b. stratified random sampling

c. convenience sampling

d. purposive sampling

31. Explain what problems (if any) the retailer may encounter with this sampling strategy.

Use the scenario below to answer questions 32 and 33.

In California's San Joaquin valley, intensive irrigation has washed selenium from the soil into the drainage channels and rivers emptying into the San Francisco Bay (selenium is toxic to animals in high concentrations). Selenium concentrations were randomly sampled in two drainage channels: channel A drains fields with intensive irrigation; channel B drains fields with moderate irrigation. Each sample contains 15 observations (samples have normal distributions). Researchers want to test if selenium concentrations are higher in channel A.

32. The hypotheses for this test are:

a. Non-directional : A = B

: A B

b. Directional : A B

: A > B

c. Directional : A B

: A > B

d. Directional : A B

: A < B

e. Non-directional : A = B

: A B

33. To reject the null hypothesis at a 99% confidence level, the test statistic must be greater than the critical t value of

a. 2.47

b. 2.76

c. 2.05

d. 1.70

e. 2.46

Use the scenario below to answer questions 34 and 35.

A researcher is studying salinity levels during spring runoff in 5 estuaries along the BC coast. Samples were taken in random selected locations within each estuary. Salinity data are assumed to be normally distributed.

34. In reviewing the data, the researcher has doubts about the reliability and accuracy of the instrument used to measure salinity. Which test can the researcher use to answer the research question?

35. The researcher wants to focus specifically on two estuaries for a portion of the study. Which test can he use to determine if significant differences exist between the two selected estuaries?

Thanks a lot for this help.

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## SOLUTION This solution is **FREE** courtesy of BrainMass!

Please see attached file for my response to your questions. I have located a very helpful guide that will be extremely helpful in doing questions such as these. I hope this helps and take care.

29.

Answer Inferential test

d One sample difference of means

b Regression

g Two or more sample Chi-square

c Spearman's

g 1 sample chi square

a 1-sample K-S

e 2 sample difference of means

30. c

31. Problem: this sample may not represent the true population of people who shop at the store. Because this is a non-probability sample, the retailer will not be able to use any inferential tests on the data. However, he could use descriptive statistics on his dataset if he wants.

32. b (directional because they are testing if the mean of sample A is greater than the mean of sample B)

33. a (at = 0.01 and df (n1+n2-2) = 15+15 -2 = 28, tc for one tailed test is 2.47).

34. Because the data are unreliable, the researcher should use a non-parametric test for multiple samples - the chi-square test which uses frequencies and categories instead of actual data values.

35. With unreliable data, the researcher should use a non-parametric test for differences between two samples - the two sample KS test (which also uses rankings). The researcher could also use the 2 or more sample Chi-square test but it would be better to downgrade to an ordinal test, rather than a nominal test (less information will be lost).

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