General Stuff

For Chapters 6 & 7. 1. Review computation of standard deviations and the generation of z-scores
2. Note Figure 6.1 on page 123, and understand conceptually the two-stage process of
inferential statistics.
3. Compare and think about the statements "By knowing the makeup of a population, we can
determine the probability of obtaining specific samples" (page 123) and "Most often the
standard deviation of the population is not known, and the standard error of sample
means cannot be computed" (page 205).
4. Understand the translation from probability to proportion (See page 124).
5. Understand why the normal distribution is a good model for naturally accurring
distributions (page 129).
6. KNOW how to use the unit table.
7. Review the hints on page 133 in regards to working probability problems.

HERE COMES THE DATA

High School Psychology Test Scores
data grades;
input student $ gender $ future_major $ score1 score2 height weight age;
cards;
1   m psyc 33 38 69 112 14
2   m psyc 29 33 56   84 13
3   f   psyc 38 40 65 98 13
4   f   psyc 27 31 62 102 14
5   f   psyc 40 35 64 103 14
6   m psyc 40 38 57 84 12
7   m math 43 40 60 85 12
8   m psyc 34 42 63 112 15
9   f   art    44 39 63 84 13
10 m psyc 40 44 60 99 12
11 m math 31 29 52 51 11
12 m psyc 28 31 64 90 14
13 f   biol   45 39 57 77 12
14 f   psyc 31 43 66 112 15
15 f   hist 42 41 72 150 16
16 f   hist 40 27 65 128 12
17 f   psyc 44 42 67 133 15
18 m psyc 41 40 57 85 11
19 m psyc 40 38 67 113 15
20 m psyc 41 35 65 145 14
;

PLEASE USE A SPREADSHEET TO PERFORM ALL CALCULATIONS
1. First compute descriptive statistics for the five variables (Please assume that
     population values are known for high school height (mu = 66; sigma = 6 ) and weight
    (mu =105 ; sigma = 25).
2. a. What is the probability of randomly selecting a male?
     b. What is the probability of randomly selecting a student who wants to be psyc
          major?
     c. If you randomly select 2 students, was is the probability that they will both be
         future history majors?
     d. If your only knowledge of the students was that they were enrolled in a high
          school course, and you did randomly select 2 students to interview, and they
          both were future history majors, what might                   you infer about the
          class content?
3. Compute z-scores for height, weight, and age.
     a. What is the probability of randomly selecting a student who is taller than 67
          inches?
     b. Compute the standard error of X-bar for the three variables.
4. A researcher believes that this group of students is over weight. Test this
      hypothesis (set alpha to .05, and use a two tailed test) using a z-zcore as the test
      statistic. The researcher also thinks the students are too short, test this hypothesis
      as above.

Here Comes Question #2

Please use the data set in question #1 and apply a one sample t-test to test
(two tailed) the hypothesis that the mean school weight, height, and age, are not 66,
105, and 11 (sigma for age is 2).

Due to circumstances out of our control the 3rd question will NOT be posted. We apologize for any inconvenience.

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by William Fuller