PSY 555 Homework 3



2.11.     The first quartile for males is approximately .77, whereas for females it is about .80.  The third quartiles are nearly equal for males and females, with a value of .87. 







2.19(c).  The mean, or the average.










2.20(d).  The variance was calculated in 2.20(b) and the standard deviation was derived in










2.28.     The amount of shock that a subject delivers to a white participant does not depend upon whether or not that subject has been insulted by the experimenter.  On the other hand, black participants do suffer when the experimenter insults the subject.




2.35.     Rats running a straight alley maze:






2.40.     The distribution of GPA is somewhat asymmetric, with B's and C's predominating.  There were few students with an A average, but none who failed all of their courses.


2.48.     Original data: 5   8    3    8    6    9    9    7




          If  then s2=cs1 and we want s2=1.00.






          Therefore, we want to divide the original scores by 2.1.


                  2.381     3.809     1.428     3.809     2.857     4.286     4.286     3.333




2.52.     Boxplot for ADDSC [Refer to stem-and-leaf in Exercise 2.15]:


          Median location=



          Hinge location=


Hinges=44.5 and 60.5




          Inner fences:  Hinges  1.5*(H-spread)=     60.5+1.5(16)=60.5+24=84.5




          Adjacent values= 26 and 78.



          20        30        40        50       60       70         80        90




               -------------------|______|_______|------------------    **



1.        Mode:     Advantages of the mode include the fact that it represents the most people/scores in your data set and the mode is also a score that actually occurred in your data set (it is a "real" score). Also, the mode is the only measure of central tendency that can be used appropriately with nominal data.  The mode depends heavily on how you group your data and the mode may not be particularly representative of all your data. 


          Median:   An advantage of the median is that it is unaffected by extreme scores.  Also, the calculation of the median does not make any assumptions about the interval properties of a measurement scale.  However, a major disadvantage of the median is that it is more difficult to use the median in equations than the mean.  Also, the median is not as stable as the mean from sample to sample.


          Mean:     Some disadvantages of the mean include the fact that it is heavily influenced by extreme scores, it is a value that may not actually exist in the data, and its use requires the assumption of an interval scale of measurement for the data.  However, the mean is advantageous in that it is easy to use algebraically.  So, it is much easier to use the mean in statistical formulas than it would be to use the median.  Also, the mean is a much more stable estimate of the population mean than is the median or the mode.


2.        Data:     7    4    5    2    5    9    4    8    3    8



7         2.25

4         2.25

5         .25

2         12.25

5         .25

9         12.25

4         2.25

8         6.25

3         6.25

8         6.25

∑X=55     50.5
















4.         is the population mean, so:


If we know =14 and that the population contains 40 scores/people, then the  can be determined by using the formula .