PSY 231 Stats/Methods I
Assignment 4
Due: At Exam 2 on 3/13
Points: 20

Part I (15 points)

his  assignment requires students to complete selected problems from the Gravetter & Wallnau statistics text (7th edition). Please use a separate sheet of paper and write legibly. Please work these problems by hand. For computational problems, please show your work and circle your final answer. 

From Chapter 2:

Q12, Q18, Q21

From Chapter 3:

Q22, Q24, Q26  

From Chapter 4:
Q10, Q16, Q22, Q24

Part II (5 points) Descriptive Statistics in SPSS

This part of the assignment requires students to use SPSS.  You will do this portion of the assignment in lab on 2/26 or 2/28.

            This exercise uses hypothetical data from a social interaction study with toddlers.  The study asked whether toddlers as young as 33 months were sensitive to whether their same-age playmate is of the same or a different sex.  Pairs of toddlers were placed together in a playroom setting and given a desirable toy to play with.  The question of interest is whether the amount of social interaction between the two is different, depending on whether the children are the same sex or different sexes.  The question might be answered by observing paired toddlers and recording how often they interact with each other.

            The data are given below for each of the two conditions.  In one condition, the 30 pairs of toddlers are the same sex. In the second condition, there are another 30 different-sex pairs.  The dependent variable is the number of social interactions that occurred in a 30-minute period.

SAME-SEX PAIRS

                                        27    25    37    31    34    28    29    25    35    30    28    32    29    30    27

                                        33    31   30    28    31    28    27    22    33    32    36    32    27    32   31

DIFFERENT-SEX PAIRS

                                        24    21    33   17    16    17    26    15    28    8   27    32    22    18  26 

                                        28    26    17    16    15    22    18    17    16    18   29    28    15    16   19

1.     Use SPSS to create a data file. (Note: You do NOT need to print this data file)
Note: There are two levels of the independent variable. We want to obtain descriptive statistics for each level of the independent variable. Therefore, use the Analyze, Descriptive Statistics, Explore command to request the information in #2. 

2.     Calculate measures of central tendency (mean, median, mode) and measures of variability (standard deviation, variance) for each set of data.  Include a box plot display and a histogram for each group. Print the output with your name and lab day in the header.

3.     Examine the output and then write a description of  the shape of the distribution for each group.

4.    On the printout, explain which measures of central tendency and variability are most appropriate to report in this situation. Be sure to address both groups.

5.    On the printout, discuss what the descriptive statistics suggest about whether there are any differences between the two conditions. In other words, what are your tentative conclusions?