Blog

A researcher conducts an experiment to determine whether moderate doses of St. John’s wort have any effect on the memory of college students.  For this study, what is the independent variable?

a) What is the main purpose of a z-score (i.e., what does it tell us?)? b) Imagine that your friend tells you her z-score on an extroversion scale is -0.50. What does this mean? Your interpretation of this score does not need to be long, but it should fully explain the score.

You have a score of X = 20 on a quiz. Which set of statistics would give you the best grade on the quiz?

Fill in the missing values. X f p % cf  c% 20 2 0.04 3.77 53 100.00 19 [value9] 0.08 7.55 51 [value8] 18 6 0.11 11.32 47 88.68 17 8 0.15 15.09 41 77.36 16 6 0.11 11.32 [value7] 62.26 15 5 [value6] 9.43 27 50.94 14 4 0.08 7.55 22 41.51 13 [value4] 0.13 13.21 18 [value5] 12 6 0.11 11.32 11 20.75 11 2 [value2] 3.77 [value3] 9.43 10 [value1] 0.06 5.66 3 5.66 Total 53 [value10]

a) Define mean. Go beyond telling me that it is a mathematical average and describe the mean in conceptual terms. b) Define median. Go beyond telling me that it is 50th percentile and describe the median in terms of the data. c) Define mode.

For the following distribution, what is the highest score?X               f20-24    215-19    510-14    4 5-9         1

Fill in the missing values. X f p % cf  c% 20 3 0.06 5.66 53 100.00 19 [value9] 0.06 5.66 50 [value8] 18 6 0.11 11.32 47 88.68 17 8 0.15 15.09 41 77.36 16 5 0.09 9.43 [value7] 62.26 15 5 [value6] 9.43 28 52.83 14 7 0.13 13.21 23 43.40 13 [value4] 0.09 9.43 16 [value5] 12 6 0.11 11.32 11 20.75 11 2 [value2] 3.77 [value3] 9.43 10 [value1] 0.06 5.66 3 5.66 Total 53 [value10]

What is a random sample and why is it important?

If every X, or raw score, is transformed into a z-score the distribution will have:

Based on the frequency polygon displayed below, the most common test grade was around