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Answers to Homework 8
2.
a)
The sample standard deviation describes the variability of the scores in the
sample. In this case, the standard distance between a score and the sample
mean is 12 points.
b)
The estimated standard error is 3 points. The standard error provides a
measure of the standard distance between a sample mean and the
population mean.
3.
a)
s
2
= SS/(n1) = 1152/91 =
144
s
M
= √s
2
/n = 144/√9 =
4
c)
s
2
= SS/(n1) = 1260/361 =
36
s
M
= √s
2
/n = 36/√9 =
1
4.
The sample variance in the t formula changes from one sample to another and
contributes to the variability of the t statistics. A zscore uses the population
variance which is constant from one sample to another.
6.
a)
t = ±2.306
c)
t = ±2.064
7.
a)
1 + 5 + 1 + 1 = 8/4 = 2
X
XM
(XM)
2
1
1
1
5
3
9
1
1
1
1
1
1
12
SS / N1 = variance
√variance = SD
12/3 = 4
√4 =2
b)
s
M
= √s
2
/n = 2/√4 =
1
8.
a)
6 + 12 + 0 + 3 + 4 = 25/5 = 5
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This note was uploaded on 01/15/2010 for the course PSYC 331 taught by Professor Dianealonso during the Fall '09 term at UMBC.
 Fall '09
 DianeAlonso

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