Module 3

Good Morning

04/11/2010 07:22:19 AM

Chapter 8 and Group Project Part 2

Module 3 - Testing Hypothesis

How are you today?

Welcome in Module 3 of our class.

This week, you need to post your Excel file with the calculation of your average study time per day. Please, reply to this Sunday Letter in the discussion area named: REPLY to my Sunday Letter and post your Excel File. Before posting your Excel file, you will need to calculate your average study time.

This is a short tutorial for calculating your average study time:

Excel:

You need to learn how to use Excel as a calculator. Select a cell, type “=” and continue with commands for calculation. Imagine that your study time (in hours) is recorded in cells d4 to d22, for example. The formula for average is:

In cell d23 print:

=average(d4:d22)

Press Enter.

If the total number of days between your first and last record is 21, then to calculate the average study time per day:

In cell d24, for example, type:

=d23/21

Press Enter. Color the cell yellow, if you want to help me.

Post your excel file as an attachment and reply to this letter.

Ask your online tutor, Joseph Babb, for more information on Excel. I will keep adding bonus for using online tutor to your grade for Module 3.

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For Part 2 of your group project, you will test my hypothesis, which I will explain in the overview for chapter 8.

The week of April 12th to April 18th, I would like you to work on WA8 and HW8.

Overview of chapter 8:

I believe that, in average, students in my class study less than 3 hours per week. This will be the first hypothesis that you will need to test for your Final Group Project. I am not saying that I know that you study in average less than 3 hours; I believe that this is the case.

In science we call our believes hypotheses.

In science we test our hypotheses indirectly; we test the opposite of what we believe.

We call our believe  ALTERNATIVE HYPOTHESIS.

We call the opposite of the alternative hypothesis NULL HYPOTHESIS.

In all sciences, we test the null hypothesis. If the null is true, we reject the alternative hypothesis. If we fail to reject the null, then we accept the alternative hypothesis.

I will go over one example that corresponds to your final project.

1.       Testing the Null hypothesis about the mean with one sample at level of significance 5% or alpha = .05:

a.       In average, my students study more than 3 hours per week. The null hypothesis can be represented mathematically like this:

Ho: μ = 3 or μ > 3

b.      Alternative hypothesis: μ < 3 hours per week.

Ha: µ < 3

c.       We do not know the standard deviation, therefore use the t-test.

                                              Formula 1

In this formula, μ is the value stated in the Null Hypothesis = > 3. You will need the standard deviation from the sample. Also, n = number of students in PSY208 after Test #2.

You compare the t-test calculated with Formula 1. If the t-test is less or equal to critical t-value, accept the null and reject the alternative hypothesis. If the t-test is more than your critical value, accept the alternative hypothesis at 5% level of significance.

 New words for chapter 8:

On the horizontal axis, CRITICAL VALUE IS THE VALUE BETWEEN BLUE AND WHITE AREA.

The area under the curve is the probability. The total area is one. The blue area in our case is .05. The white area is .95. If our test value is UNDER THE WHITE AREA, ACCEPT THE NULL HYPOTHESIS AND REJECT ALTERNATIVE HYPOTHESIS.

1.      p-value (blue area, p-value is probability)

2.      Z-test (if you know sigma, use Z-test)

3.      t-test (Don't know sigma, use t-test - Formula 1)

4.      Degrees of freedom for t-test - df = n-1

5.     Level of significance - α, is the probability presented by the blue area.

6. Critical value for specific level of significance (You know that alpha is 5%. What is the t-value that corresponds to the vertical line between the white and blue area? Well, use the table for t-values.)    

7.      Non-directional (two-tail) and one-directional (one-tail) hypotheses

8.      Confidence Interval (CI) and testing the null-hypothesis with CI

I hope that your will have your WA8 and HW8 on time to the end of this week.

Have a nice day.

Dr. Fuller