HW5 - Chapter 9 The Basics of Experimentation and Testing...

Chapter 9. The Basics of Experimentation and Testing for a Difference Between Means
Name:
Class:
Date:
From Kiess and Green’s Statistical Concepts for the Behavioral Sciences , 4/e
Assignment 9.1
The purpose of this assignment is to help you to become more comfortable in recognizing
what each statistical symbol and formula in Chapter 9 represents. For each item in the
table below, either the term or the definition is given. Complete the table with the missing
information. For example, for the between-subjects design , write the definition in the
appropriate column. It is best to complete this page without looking at your notes or
textbook. Once you have completed it, refer back to your notes and textbook to verify
you are correct.
Term Definition
Between-subjects design
Within-subjects design
The probability of failing to find a statistically significant
difference when one is actually there
Obtaining subjects from among people who are accessible or
convenient to the researcher
Extraneous variables
The amount a sample mean differs from its population mean
Confound
Groups in which the subjects are not expected to differ in any
systematic or consistent way
Alternative hypothesis
Standard deviation of a theoretical sampling distribution of
12
X X −
Random assignment
Developed for measuring the effect of the independent
variable on the dependent variable
Statistically significant
difference

Chapter 9. The Basics of Experimentation and Testing for a Difference Between Means
Name:
Class:
Date:
From Kiess and Green’s Statistical Concepts for the Behavioral Sciences, 4/e
Assignment 9.2
The data sets below provide scores obtained from two independent groups of subjects,
each group was given a different treatment condition, X
1
and X
2
, respectively. For each
data set, calculate a t test for independent groups. Then indicate the decisions you would
make for the statistical hypotheses. If you do find a statistically significant difference,
calculate the size of that effect.
Set A Set B Set C
X
1
X
2
X
1
X
2
X
1
X
2
43 39 15 13 540 400
50 37 14 14 460 415
61 35 11 15 600 440
60 38 13 13 520 430
58 40 12 15 430 420
49 36 13 460
Set D Set E Set F
X
1
X
2
X
1
X
2
X
1
X
2
91 101 100 98 3 5
92 105 101 105 5 4
95 102 102 110 4 3
96 107 98 96 3 5
98 99 98 5 3

Chapter 9. The Basics of Experimentation and Testing for a Difference Between Means
Set E
X
1
X
2
100 98
101 105
102 110
98 96
99 98
Sum 500 507
n 5 5
X
100.0 101.4
SS 10 139.2
s 2
2.5 34.8
df 8
t –0.51
Fail to reject H
0
Do not accept H
1
No need to calculate
2
η
If you are having trouble figuring out why you obtained an incorrect answer, it helps to know where to look
for errors. If your answer doesn’t match with the answer listed here, check the following:
• Did you include all of the correct values?
• Did you take the square root of the entire denominator?