PSY 555 Homework 3

Answers

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(a). _{}

_{}

2.19(b). _{}

2.19(c). The mean, or the average.

2.20(a). _{}

_{}

2.20(b). _{}

2.20(c). _{}

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

2.20(c).

2.21(a). _{}_{}

2.21(b).

_{}

2.21(c). _{}

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.

2.30.

2.35. Rats
running a straight alley maze:

_{}_{}

Median=21

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

s_{1}=2.1

If
_{} then s_{2}=*c*s_{1 }and we want s_{2}=1.00.

s_{2}=*c*s_{1}

_{ }1=*c*(2.1)

*c*=1/2.1

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

s_{2}=2.1

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

Median
location=_{}

Median=50

Hinge
location=_{}

Hinges=44.5
and 60.5

H-spread=60.5-44.5=16

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

and

44.5-1.5(16)=44.5-24=20.5

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

N=10

_{}

_{}

_{}

_{}

3. _{}

_{}

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 _{}.

_{}

_{}

So, _{}