A researcher conducts an independent-measures study examining how the brain chemical serotonin is related to aggression. One sample of rats serves as a control group and receives a placebo that does not affect normal levels of serotonin. A second sample of rats receives a drug that lowers brain levels of serotonin. Then the researcher tests the animals by recording the number of aggressive responses each of the rats display. The data are as follows. Control Low Serotonin n = 15 n = 20 M = 18 M = 22 SS = 172.5 SS = 135.0 a. What research design was used to answer this question? b. What was the scale of measurement for the dependent variable? c. What was the scale of measurement for the independent variable? d. Does the drug have a significant effect on aggression? Use an alpha level of .05, two tails. e. Compute r2 and write an interpretation of the result.
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 conducts an independent-measures study examining how the brain chemical serotonin is related to aggression. One sample of rats serves as a control group and receives a placebo that does not affect normal levels of serotonin. A second sample of rats receives a drug that lowers brain levels of serotonin. Then the researcher tests the animals by recording the number of aggressive responses each of the rats display. The data are as follows.
Control Low Serotonin
n = 15 n = 20
M = 18 M = 22
SS = 172.5 SS = 135.0
a. What research design was used to answer this question?
b. What was the scale of measurement for the dependent variable?
c. What was the scale of measurement for the independent variable?
d. Does the drug have a significant effect on aggression? Use an alpha level of .05, two tails.
e. Compute r2 and write an interpretation of the result.
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