Statistics Questions

[Jeanlouisincog]

These are some very basic statistic questions that I am struggling to answer at the moment. Any help will be greatly appreciated.

Question 2) Suppose that the distribution of marks on an exam is closely described by a normal curve with a mean of 65. The 84th percentile of this distribution is 75. (a) What is the 16th percentile? (b) What is the approximate value of the standard deviation of exam marks? (c) What z score is associated with an exam mark of 50? (d) What percentile corresponds to an exam mark of 85? (e) Do you think there were many marks below 35? Explain.
Question 3) (a)A sample consisting of four pieces of luggage was selected from among those checked at an airline counter, yielding the following data on x = weight (in pounds): x1 = 33.5, x2 = 27.3, x3 = 36.7, x4 = 30.5 2 Suppose that one more piece is selected; denote its weight by x5. Find a value of x5, other than 32, such that ¯x = sample median.
(b) An instructor has graded 19 exam papers submitted by students in a class of 20 students, and the mean mark so far is 70. (The maximum possible mark is 100.) How high would the mark on the last paper have to be to raise the class mean by 1 mark? By 2 marks?
Question 5: The following data are the ages (in years) at diagnosis for 20 patients under treatment for meningitis: 18 18 25 19 23 20 69 18 21 18 20 18 18 20 18 19 28 17 18 18 (a) Calculate and interpret the values of the sample mean, variance, and standard deviation. (b) Compute the 10% trimmed mean and the sample median. Why might you recommend either one of these two statistics as measures of centre rather than the sample mean? (c) Compute the upper quartile, the lower quartile, and the interquartile range.

 

[tkhunny]

You're going to have to learn to use a calculator or spreadsheet or a table.

 

[Dr.Peterson]

These are some very basic statistic questions that I am struggling to answer at the moment. Any help will be greatly appreciated.

Question 2) Suppose that the distribution of marks on an exam is closely described by a normal curve with a mean of 65. The 84th percentile of this distribution is 75. (a) What is the 16th percentile? (b) What is the approximate value of the standard deviation of exam marks? (c) What z score is associated with an exam mark of 50? (d) What percentile corresponds to an exam mark of 85? (e) Do you think there were many marks below 35? Explain.
Question 3) (a)A sample consisting of four pieces of luggage was selected from among those checked at an airline counter, yielding the following data on x = weight (in pounds): x1 = 33.5, x2 = 27.3, x3 = 36.7, x4 = 30.5 2 Suppose that one more piece is selected; denote its weight by x5. Find a value of x5, other than 32, such that ¯x = sample median.
(b) An instructor has graded 19 exam papers submitted by students in a class of 20 students, and the mean mark so far is 70. (The maximum possible mark is 100.) How high would the mark on the last paper have to be to raise the class mean by 1 mark? By 2 marks?
Question 5: The following data are the ages (in years) at diagnosis for 20 patients under treatment for meningitis: 18 18 25 19 23 20 69 18 21 18 20 18 18 20 18 19 28 17 18 18 (a) Calculate and interpret the values of the sample mean, variance, and standard deviation. (b) Compute the 10% trimmed mean and the sample median. Why might you recommend either one of these two statistics as measures of centre rather than the sample mean? (c) Compute the upper quartile, the lower quartile, and the interquartile range.

It's hard to know how to help you without any clue as to what you do know about these topics.

Please pick one of these questions to start with, and tell us your understanding of what you are given and what you have to do. If you can do any part of a problem, show us what you did, even if you are sure it is not leading toward the solution. If you have specific questions, like "what does 84th percentile mean?", that will help us focus our attention where you need it.