STAT prob DOCX

Title	STAT prob
Author	Bob Johnson
Pages	2
File Size	18 KB
File Type	DOCX
Total Downloads	412
Total Views	650

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1. In a time motion study, it was found that a certain manual work can be finished at an average time of 40 minutes with a standard deviation of 8 minutes. A group of 16 students is given a special training and then found the average is only 35 minutes. Can we conclude that the special training can speed up the work using 0.01 level? 2. A standardized test was administered to thousands of students with a mean score of 85 and a standard deviation of 8. A random sample of 50 students were given the same test and showed an average of 83.20. Is there an evidence to show that this group has a lower performance than the ones in general at 0.05 level? 3. In the certain studies of deception among students the scores achieve on tests given under conditions in which cheating was possible were compared with scores achieve by the sample students under strictly supervised conditions. In a certain test given under "honest" conditions the mean score of 25 sample students is 62 and the standard deviation is 10. A student who took the test under non-supervised conditions turned a mean score of 87. What conclusion can be drawn out of the given information at 0.01 level of significance. 4. An Algebra teacher wants to compare two methods of teaching Algebra. One is the lecture method and the other is the personalized system of instruction (PSI method). Students are paired by matching those with similar mathematics background and performance. A random sample of 11 pairs is selected. From each pair, one student is randomly chosen to take the lecture course: the other student takes the PSI course. Both courses are taught by the Algebra teacher. The final grades for the 11 pairs of students are found to be the following: Lecture 66 93 36 84 60 66 80 73 74 83 53 PSI 67 73 35 85 64 57 79 70 67 79 50 Do the data provide sufficient evidence to conclude that there is a significant difference in the mean student performance between the two instructional methods? Use a significance level of 0.05. 5. A study is made to determine if a cold climate contributes more to absenteeism from school during December than a warmer climate. Two groups of students are selected at random, one group from Baguio and the other from Metro Manila. Of the 300 students from Baguio, 72 were absent at least one day during December, and of the 400 students from Metro Manila, 70 were absent one or more days. Can we conclude that a colder climate, results in a greater proportion of students being absent from school at least one day during December? Use 0.01 level of significance. 6. A manufacturer of calculator batteries claims that the life of his batteries are approximately normally distributed with a standard deviation equal to 0.9 year. If a random sample of 10 of these batteries have a standard deviation of 1.2 years. Do you think that s > 0.9 year? Use a 0.05 level of significance. 7. The standard deviation of a distribution is hypothesized to be 50. If an observed sample of 16 yields a variance of 57, we should reject the null hypothesis that the true variance is 50? Use a 0.05 level of significance....