Hypothesis testing about if relaxation reduces headaches
Not what you're looking for?
A researcher would like to determine if relaxation training will affect the number of headaches for chronic headache sufferers. For a week prior to training, each participant records the number of headaches suffered. Participants then receive relaxation training, and for the week following training the number of headaches is again measured. The change in number of headaches before and after training is as follows (minus signs indicate a reduction).
Difference scores: -5 -1 -4 -3 -6 -8 0 +1 -1
(a) Compute the mean and SS for the sample of difference scores.
MD = ______
SS = ________
(b) Do the results indicate a significant difference? Use a two-tailed test with α = .05.
A. Yes, the relaxation training has a significant effect.
B. No, the relaxation training hasn't any significant effect.
(c) Compute r2, the percentage of variance accounted for, to measure the size of the effect. (Round the answer to two decimal places.)
r2 = _______
Purchase this Solution
Solution Summary
How to test a hypothesis about whether relaxation training affects the number of chronic headaches?
Solution Preview
a)
Number of observations = 9
The mean = [-5 + -1 + -4 + -3 + -6 + -8 + 0 + 1 - 1]/9 = -27/9 = -3
SS = sum of the squares of the difference between observations and mean.
= (-5 - (-3))^2 + (-1 - (-3))^2 +............(-1 - (-3))^2 , where ^ means raised to the power of
Thus, SS in this case = 72
b)
We perform a 1 sample t test to see if the mean of the difference is significantly different from 0.
Independent one-sample t-test
In testing the null hypothesis that the population mean is equal to a specified value μ0, one uses the statistic
t = (x - μ0)/(s/n^0.5)
where x is sample mean and s is the sample standard deviation of the sample and n is the sample size.
The degrees of freedom used in this test is n − 1.
p value can be found from a student's t table.
DF 0.200 0.100 0.0500 0.0200 0.0100 0.00500 0.00200 0.001 -> p values
1 3.078 6.314 12.706 31.820 63.657 127.321 318.309 636.619
2 1.886 2.920 4.303 6.965 9.925 14.089 22.327 31.599
3 1.638 2.353 3.182 4.541 5.841 7.453 10.215 12.924
4 1.533 2.132 2.776 3.747 4.604 5.598 7.173 8.610
5 1.476 2.015 2.571 3.365 4.032 4.773 5.893 6.869
6 ...
Purchase this Solution
Free BrainMass Quizzes
Measures of Central Tendency
This quiz evaluates the students understanding of the measures of central tendency seen in statistics. This quiz is specifically designed to incorporate the measures of central tendency as they relate to psychological research.
Measures of Central Tendency
Tests knowledge of the three main measures of central tendency, including some simple calculation questions.
Terms and Definitions for Statistics
This quiz covers basic terms and definitions of statistics.
Know Your Statistical Concepts
Each question is a choice-summary multiple choice question that presents you with a statistical concept and then 4 numbered statements. You must decide which (if any) of the numbered statements is/are true as they relate to the statistical concept.