A little extra practice for Exam 2 and a few things to consider.

Chapter 7.

Make sure that you can identify the various graphs and tables presented in chapter 7 and that you can interpret each. Know the terms to remember on page 154.

Chapter 8.

Excluding Spearman’s r, be sure that you understand and can explain in your own words the terms to remember on page 191.

Below are the amounts of ice cream sold and the number of drownings for each day.

Day / Ice cream(X) / Drownings(Y)
1 / 7 / 8
2 / 5 / 4
3 / 6 / 5
4 / 4 / 5
5 / 9 / 9
6 / 10 / 11
7 / 11 / 12
8 / 12 / 13
9 / 13 / 15

Draw a scatterplot of the scores. Based on the scatterplot does there appear to be a correlation between the two variables? Why do you say this?

Be sure you can calculate the correlation between these variables using the different methods we explored in class. If given the SS for X and Y could you calculate the correlation for the two variables? What else would you need?

According to Cohen what is the size of this correlation?

Know the definitional and computational formulas for covariance.

Know how to calculate a correlation when given the covariance.

Know the computational formula for correlations.

If given the Z scores of two variables be able to calculate the correlation of the two variables.

What proportion of variance in Y is accounted for by X?

The researcher wants to make the claim that ice cream sales cause drownings. What do you have to say about this? What error is the researcher making? Can you think of a third variable that would explain this relationship?

What if greatermeasurement error was present in either or both variables?

Chapter 10.

Know and be able to explain in your own words the terms to remember on page 254.

Know and be able to apply the rules that were provided with the ABC’s of probability handout.

Which rule would you apply to the following problem?

Bill and Fred missed a statistics quiz because they went to see Aerosmith in concert. They tell their professor that they missed the quiz because Bill's car had a flat tire and could not get back to the campus on time. The professor agrees to give a make up quiz and sends Bill and Fred to separate rooms with a new quiz. Bill and Fred find that the quiz is a single question "You will be given full credit for the quiz if you both tell which tire was flat and you both agree." Assuming independence, what is the probability that Bill and Fred will receive credit for the quiz? Provide the rationale for your answer.

Given a table that describes a sample be able to calculate the joint(e.g., P(A∩B), marginal (e.g., P(A), conditional (e.g., P(A|B) and union (e.g., P(AUB). Be able to explain what each describes.

Party Affiliation
Republican / Democrat / Total
Male / 100 / 20 / 120
Female / 20 / 60 / 80
Column total / 120 / 80 / 200

Know how to calculate probabilities for a binomial distribution.

Chapter 11.

Know and be able to explain in your own words the terms to remember on page 288

What are null and research (alternative) hypotheses?

What is α?

What is a critical z value?

What does it mean to say that test is statistically significant?

When do you use a two-tailed test?

If α = .05, what is the critical z a two-tailed? What if α = .01?

Be able to explain the propositions associated with the Central Limit Theorem.

Why do we use samples in statistics?

Know the characteristics of the distribution of means.

What does the standard error of the distribution of means represent?

How is the distribution of means used in hypothesis testing?

Know how to calculate the standard error of the mean.

Know how to test a sample against a known population value (µ) using the hypothesis testing steps provided in class.

Know how to calculate a 95% and 99% confidence interval.

Chapter 12

One-sample z-test

Let's suppose that we know that in a population of third graders, the mean of a reading test is 100 and the standard deviation is 15. We draw a sample of 100 children, give them a new reading program and find that their mean is 92 and their standard deviation is 14.14. Did the new reading program change their scores from the population?Using the format provided in class test the null hypothesis using the appropriate statistical test. Create a 95% confidence interval, is the null hypothesis contained in this interval? Create a 99% confidence interval, is the null hypothesis contained in this interval? What does it mean if the null hypothesis value is contained in the interval? Why do we calculate confidence intervals? If we used a smaller sample what would happen to the confidence interval? A larger sample?