sales than stores in other conditionsReason: rejecting the null simply means that at least the average for one group is different from others, but didn’t say which group42Tests of Differences
1. One Sample
2. Two Independent
Samples
3. Paired
Samples
4. More Than
Two Samples
Which t test to use? It depends on (1).
the number of variables and (2). Number
of groups involved
t tests
ANOVA
43

15
•
One-Sample t-test
–
One sample
•
Independent Samples t-test
–
Two independent samples
•
Paired samples t-test
–
Two dependent samples
•
ANOVA
–
Two or more samples
Summary
Average temperature in
August = 17
°
Sales in store A = Sales in
store B
Knowledge of statistics
after class = before class
Average fuel prices in
suburbs A,B and C are
different
44
Today’s agenda
45
•
Hypothesis testing – tests of differences
–
Different types of t tests
–
Two-tailed vs. one-tailed test
– ANOVA
•
How to write about hypothesis testing
•
A few words on assignment 2
How to write about hypothesis testing – the
formulaic approach
• 1
st
step – describe the test
– Which test did you use?
– What variables are involved?
–
What are the groups involved?
• 2
nd
step – describe the test results
– What did you conclude (reject or not reject the null)?
–
What is the p value?
– What does it mean in plain English?
46

16
A (type of t test) _____ was conducted to compare the difference between
(group or variable 1) _____ and (group or variable 2) _____ in/for (variable or
group name) _____.
in our case this is as follows:
An independent samples t test was conducted to compare the difference
between teenagers and adults in their mean preference before entering the
theme park.
Or
A paired sample t test was conducted to compare the mean preference
before and after visiting the theme park
Describing the test - t test
47
A one-way between subjects ANOVA was conducted to compare the
effect of (IV) _____ on (DV) _____.
in our case this is as follows:
A one-way between subjects ANOVA was conducted to compare the
effect of different promotion programs on average store sales.
Describing the test – one way ANOVA
48
There was a significant (or not a significant) difference in (variable(s)) _____
between (groups) _____ at the p<.05 level [p = ____].
(group 1) _____ exhibit higher (or lower) (variable name) _____ than (group
2) _____ .
in our case this is as follows:
The null hypothesis is rejected. There is a significant difference in preference
before entering the park between teenagers and adults [p = .006].
Teenagers exhibit higher average preference before entering the park than
adults.
(copy/paste the SPSS output tables here)
Describing the results – t test
49

17
There was a significant (not a significant) effect of IV _____ on DV
_____ at the p<.05 level for (the number of) _____ conditions [p =
____].
in our case this is as follows:
The null hypothesis is rejected. There is a significant effect of
promotion on store sales at the p<.05 level for the three conditions [p
= .001].
(copy/paste the SPSS output tables here)
Describing the results – one way
ANOVA
50
Today’s agenda
51
•
Hypothesis testing – tests of differences
–
Different types of t tests
–
Two-tailed vs. one-tailed test
– ANOVA
•
How to write about hypothesis testing
•
A few words on assignment 2
What is expected of the assignment?

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- Two '16
- Statistics, Null hypothesis, Statistical hypothesis testing, Statistical tests, Student's t-test