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Chapter 10: Q.132 (page 610)
A new SAT study course is tested on individuals. Pre-course and post-course scores are recorded. Of interest is the mean increase in SAT scores. The following data are collected:
The given data is an independent group means, population standard deviations and/or variances known.
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89. Suppose a statistics instructor believes that there is no significant difference between the mean class scores of statistics day students on Exam 2 and statistics night students on Exam 2. She takes random samples from each of the populations. The mean and standard deviation for 35 statistics day students were 75.86 and 16.91. The mean and standard deviation for 37 statistics night students were 75.41 and 19.73. The "day" subscript refers to the statistics day students. The "night" subscript refers to the statistics night students. A concluding statement is:
a. There is sufficient evidence to conclude that statistics night students' mean on Exam 2 is better than the statistics day students' mean on Exam 2.
b. There is insufficient evidence to conclude that the statistics day students' mean on Exam 2 is better than the statistics night students' mean on Exam 2.
c. There is insufficient evidence to conclude that there is a significant difference between the means of the statistics day students and night students on Exam 2.
d. There is sufficient evidence to conclude that there is a significant difference between the means of the statistics day students and night students on Exam 2.
A study was conducted to investigate how effective a new diet was in lowering cholesterol. Results for the
randomly selected subjects are shown in the table. The differences have a normal distribution. Are the subjects鈥�
cholesterol levels lower on average after the diet? Test at the level.
| Subject | A | B | C | D | E | F | G | H | I |
| Before | 209 | 210 | 205 | 198 | 216 | 217 | 238 | 240 | 222 |
| After | 199 | 207 | 189 | 209 | 217 | 202 | 211 | 223 | 201 |
Two computer users were discussing tablet computers. A higher proportion of people ages to use tablets than the proportion of people age and older. Table localid="1653641949025" details the number of tablet owners for each age group. Test at the localid="1653641953436" level of significance.
Table.localid="1653641957518"
| localid="1653641961619" years old | localid="1653641966431" years old and older | |
| Own table | 69 | 231 |
| Sample size | 628 | 2309 |
Mean entry-level salaries for college graduates with mechanical engineering degrees and electrical engineering degrees are believed to be approximately the same. A recruiting office thinks that the mean mechanical engineering salary is actually lower than the mean electrical engineering salary. The recruiting office randomly surveys \(50\) entry level mechanical engineers and \(60\) entry level electrical engineers. Their mean salaries were \(\$46,100\) and \(\$46,700\), respectively. Their standard deviations were \(\$3,450\) and \(\$4,210\), respectively. Conduct a hypothesis test to determine if you agree that the mean
entry-level mechanical engineering salary is lower than the mean entry-level electrical engineering salary.
Use the following information to answer the next five exercises. A researcher is testing the effects of plant food on plant growth. Nine plants have been given the plant food. Another nine plants have not been given the plant food. The heights of the plants are recorded after eight weeks. The populations have normal distributions. The following table is the result. The researcher thinks the food makes the plants grow taller.
What is the p-value?
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