Dr. Jill Biden has been teaching a seventh grade English composition class for many years. She has the feeling that over the past several years, the writing ability of students has changed. A national test of proficiency in composition was administered 5 years ago. The resulting distribution of scores was normally shaped, had a mean of 85 and a standard deviation of 10.9. In order to test his feeling, she gives her present class of 43 students the same proficiency test. The resulting mean is 80 and the standard deviation is 8.7. a. What is the alternative hypothesis? b. What is the null hypothesis? c. What is your conclusion, using an alpha of 0.05 (2 tailed). d. What type of error might you be making because of your conclusion in part c
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.
Dr. Jill Biden has been teaching a seventh grade English composition class for many years. She has the feeling that over the past several years, the writing ability of students has changed. A national test of proficiency in composition was administered 5 years ago. The resulting distribution of scores was normally shaped, had a mean of 85 and a standard deviation of 10.9. In order to test his feeling, she gives her present class of 43 students the same proficiency test. The resulting mean is 80 and the standard deviation is 8.7.
a. What is the alternative hypothesis?
b. What is the null hypothesis?
c. What is your conclusion, using an alpha of 0.05 (2 tailed).
d. What type of error might you be making because of your conclusion in part c?
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