Problem Set 3.3: z Test

Criterion: Calculate a      z test to make a decision about      a sample.
Data: The average      (mean) height for adult women is 65 inches, and the standard deviation is      3.5 inches. Given the women you know, you think this number is low; so,      you record the heights of 25 of your female friends. The average height of      your 25 friends is 66.84 inches.

Portion of the Normal Curve Table





























Instruction: Answer this:      If your friends are just a representative sample of adult females,      what is the probability that your friends are so tall?


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Problem Set 3.4: Independent Variables (IVs) and Dependent Variables (DVs)

Criterion: Differentiate between independent and      dependent variables.
Data: A      researcher randomly assigns a group of adults to one of two diets plans      (Diet Plan A or Diet Plan B), and she then measures the amount of weight      loss each experiences in a two-week period.
Instruction: Answer the following: 

What is the IV in this study?
What is the DV in this study?


Problem Set 3.5: Hypotheses 

Criterion: Write a directional-alternative hypothesis,      nondirectional-alternative hypothesis, and null hypothesis.
Data: A researcher is studying      whether the amount of weight loss differs in participants who follow Diet      Plan A versus those who follow Diet Plan B.
Instruction: Write the following:

a. A directional alternative hypothesis.
b. A nondirectional alternative hypothesis.
c. The null hypothesis.

Problem Set 3.6: Errors and Significance: Type 1 and Type 2 Error

Criterion: Differentiate between Type 1      and Type 2 error.
Data: It is an established fact that in      the general population, men weigh more on average than women. In a study,      you randomly sample 100 men and 100 women, you record each participant’s      weight, and you find that there is no significant difference in weight      based on gender.
Instruction: Answer the      following:

Given that a difference       really does exist in the population, what type of error is this (Type 1       or Type 2)? Explain your answer.


Problem Set 3.7: Errors and Significance: Type 1 and Type 2 Error

Criterion: Differentiate between Type 1      and Type 2 error.
Data: In general, men and women do not      differ on IQ. However, as part of your study, you found that women scored      significantly higher than men on IQ.
Instruction: Answer the      following:

Given       that you found a difference in your study where none exists in the       general population, identify the error (Type 1 or Type 2) and explain       your answer.

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Problem Set 3.8: Hypothesis Testing and the z Score.

Criterion: Evaluate a null hypothesis based on      analysis of data.
Data: Joan      is 72 inches tall. The average (mean) height for adult women is 65 inches,      and the standard deviation is 3.5 inches.

a. State the null hypothesis.
b. State the alternative hypothesis.
c. Answer this: Joan is taller than what percentage of women in the population? (Hint: Think z score and area under the normal curve.)
d. Answer this: Given Joan’s height as compared to the population mean, do you expect to reject the null hypothesis? Explain your answer.
Problem Set 3.9: One-Sample t Test
Criterion: Hand calculate a one-sample t test.
Data: Rex’s Flower Shop advertised fresh cut roses that last longer than other roses. The mean vase life for a rose is 8 days. The following is a sample of the number of vase life days for 9 bouquets of roses from Rex’s Flower Shop: 8, 6, 12, 11, 8, 9, 14, 15, 10.
Instruction: Complete the following:
a. State the nondirectional hypothesis.
b. State the critical t for α = .05 (two tails).
c. Calculate t. Show your work.
d. Answer: Is the vase life of Rex’s roses significantly different than the population mean? Explain.

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