Students were asked what grades they usually get in school. For twelfth-grade students who responded to this question and the question about how often they wear seatbelts when driving, a summary of frequency counts for combinations of responses to the two questions is as follows. Wears Seatbelt Usual School Grades A and B C D and F Total Never 55 40 17 112 Rarely 129 95 21 245 Sometimes 168 109 9 286 Most times 290 129 25 444 Always 1,059 305 50 1,414 Total 1,701 678 122 2,501 (a) The total number of students in the table is 2,501. What percentage of these 2,501 students said that they usually get A's and B's in school? (Round your answer to one decimal place.) % (b) What percentage of the 1,701 students who said that they usually get A's and B's said that they always wear a seatbelt when driving? (Round your answer to one decimal place.) % (c) What percentage of the 678 students who said that they usually get C's said that they always wear a seatbelt when driving? (Round your answer to one decimal place.
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.
Wears Seatbelt |
Usual School Grades | |||
---|---|---|---|---|
A and B | C | D and F | Total | |
Never | 55 | 40 | 17 | 112 |
Rarely | 129 | 95 | 21 | 245 |
Sometimes | 168 | 109 | 9 | 286 |
Most times | 290 | 129 | 25 | 444 |
Always | 1,059 | 305 | 50 | 1,414 |
Total | 1,701 | 678 | 122 | 2,501 |
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