A researcher studies the effect of frequent testing on retention of class material. In one of the professor’s sections, students are given quizzes each week. The second section receives only two tests during the semester. At the end of the semester, both sections receive the same final exam, and the scores are summarized below. Frequent quizzes Two exams n = 15 n = 15
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 studies the effect of frequent testing on retention of class material. In one of
the professor’s sections, students are given quizzes each week. The second section receives
only two tests during the semester. At the end of the semester, both sections receive the
same final exam, and the scores are summarized below.
Frequent quizzes Two exams
n = 15 n = 15
M = 72 M = 68
(a) If the first sample variance is s
2 = 8 and the second sample variance is s
2 = 7,
do the data indicate that testing frequency has a statistically significant effect on
performance? Use a two-tailed test with α = .01.
(b) If the first sample variance is s
2 = 32 and the second sample variance is s
2 = 28,
do the data indicate that testing frequency has a statistically significant effect on
performance? Use a two-tailed test with α = .01.
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