Course News.....Psyc205/Soc205.....Vernoy

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Spring, 2008

I am not currently teaching Behavioral Science Statistics.

Please feel free to use this website as a tutorial.

Chapter 12
Hint: Always remember to state your null hypothesis and your research hypothesis before you begin your t-test. You need the research hypothesis to tell if you have a one-tail or two-tail test.

Hint: Remember that there are two different formulas for a single sample t-test. One formula uses the population standard deviation to compute the standard error of the mean and the other uses the sample standard deviation to compute an estimate of the standard error of the mean. Remember always use the population standard deviation if it is given to you.

Hint: Remember that the degrees of freedom are n-1 for single sample t-tests, (n₁-1)+(n₂-1) for the independent samples t-test, and n-1 for a t-test for correlated samples. (Also remember that with correlated samples n is the number of pairs.)
Chapters 8 & 9

Hint: Computing the correlation coefficient from the beginning takes a lot of time. I suggest that you budget at least 45 minutes to an hour for each problem.   This should give you enough time to carefully compute and double check all the sums and formulas.

Hint:     Remember to keep the pairs together when computing the covariance and the correlation coefficient.
            If you break up or rearrange the pairs your calculations will be totally wrong.

Hint:    Remember that a correlation between two variables means that they are related in some way, but it does not mean that X is caused by Y or that Y is caused by X!

Hint: Remember that all predictions must be accompanied by the standard error of the estimate. A prediction without the standard error of the estimate is wrong!
Chapter 7

Hint: There are no specific hints for chapter 7. Just make sure you understand all the worked problems.
Chapter 6

Hint:    The standard deviation does not change if you add or subtract a constant from every score.

Hint: Both the mean and standard deviation change if you multiply or divide every score by a constant.

Hint:    Subtracting the mean from each score then dividing each score by the standard deviation
            creates Z scores that have a mean of 0 and a standard deviation of 1.
Chapter 5
There are no hints for Chapter 5
Chapter 4

Hint: Remember to rank the scores before you find the median.
You are likely to get the wrong median if you do not rank first.

Hint: Remember that there are two middle scores if n is even.

Chapter 3

Histogram
Hint: Remember that all the bars are equal width with the X values at the real limits and
            the height at the frequency of the interval.

Hint: Remember that the graph is unreadable without proper labels.
            If you leave off just one of the labels the entire graph is wrong

Frequency Polygon
Hint: Remember that to plot a Frequency Polygon you must first generate the two extra class intervals.

Hint: Remember that all the points must be plotted at the midpoint

Hint: Remember to connect the points with straight lines.

Hint: Remember that without the proper labels the entire graph is wrong.

Cumulative Percent Polygon
Hint: The Cumulative Percent Polygon starts at C% = 0 and climbs to C% = 100.

Hint: Remember that to plot a Cumulative Percent Polygon you must first
            generate an extra class interval at the bottom.

Hint: Remember that all the points must be plotted at the upper real limit.

Hint: Remember to connect the points with straight lines.

Hint: You do not bring the graph down to the X axis after the last class interval.

Hint: Remember that without the proper labels the entire graph is wrong.

Relative Frequency Polygon
Hint: Remember that Relative Frequency Graphs always have two lines.

Hint: Remember that to plot a Relative Frequency Polygon you must first generate the
            two extra class intervals.

Hint: Remember that all the points must be plotted at the midpoint

Hint: Remember to connect the points with straight lines.

Hint: Remember that without the proper labels the entire graph is wrong.
            This also means that you must somehow distinguish between the two different lines.
            Use different markers or different colors for the different lines.
Chapter 2

Hint: Always remember to choose a class interval size (i) that is easy to count by.

Hint: Remember that the lowest class interval must contain the lowest score and
the highest class interval must contain the highest score.

Hint: The Apparent Limits do not have to be equal to the highest or lowest scores,
but all the lower apparent limits must be a multiple of the class interval size.

Buy your book as soon as possible and begin reading the first couple of chapters. It will be impossible for you to survive this course unless you read the book. All homework assignments will come from the problems at the end of the chapters in the book.
Read pages 4-6 in the textbook for detailed hints on how to do well in the course.
Do not get behind in your homework or your reading. This course is cumulative and a misunderstanding at any point can cause large problems down the road.
If you do not understand something GET HELP! E-mail Dr. Vernoy, call Dr. Vernoy, go to the Tutoring Center, come to Dr. Vernoy's office. (Click on class outline at the top of the page for office location and telephone number.)
Remember to read every word of every chapter. As you read the chapter, work all the problems and make sure you can answer the questions in each Concept Quiz. Work as many of the problems at the end of the chapter as you can. (The answers to the odd numbered problems are at the back of the book.) Make up your own problems and solve them.
The best way for everyone to learn statistics is to work problems....There are no shortcuts.

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