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 number of headaches before and after training are provided in the table. a. Compute the appropriate mean and SS. b. Do the results indicate a significant difference? Use a two-tailed test with a = .05. Include the null hypothesis in symbols, critical region(s), and a conclusion about significance. c. Compute Cohen’s d and r2 and state the size of each effect.
Inverse Normal Distribution
The method used for finding the corresponding z-critical value in a normal distribution using the known probability is said to be an inverse normal distribution. The inverse normal distribution is a continuous probability distribution with a family of two parameters.
Mean, Median, Mode
It is a descriptive summary of a data set. It can be defined by using some of the measures. The central tendencies do not provide information regarding individual data from the dataset. However, they give a summary of the data set. The central tendency or measure of central tendency is a central or typical value for a probability distribution.
Z-Scores
A z-score is a unit of measurement used in statistics to describe the position of a raw score in terms of its distance from the mean, measured with reference to standard deviation from the mean. Z-scores are useful in statistics because they allow comparison between two scores that belong to different normal distributions.
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 number of headaches before and after training are provided in the table.
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a. |
Compute the appropriate |
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b. |
Do the results indicate a significant difference? Use a two-tailed test with a = .05. Include the null hypothesis in symbols, critical region(s), and a conclusion about significance. |
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c. |
Compute Cohen’s d and r2 and state the size of each effect. |
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Before |
After |
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7 |
2 |
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3 |
2 |
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7 |
3 |
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4 |
1 |
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11 |
5 |
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13 |
5 |
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6 |
6 |
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7 |
8 |
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11 |
10 |
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