National open university of nigeria introduction to econometrics I eco 355

Experiment 1 
Experiment 2 
Sample Mean = 13 Sample Mean = 16.5 
(IV). Evaluate Null Hypothesis
:
We calculate Z for each experiment, and then look up the P value for the obtained Z, and 
make a decision. Here's what happens for each experiment:
Experiment 1 
Experiment 2 

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Sample Mean = 13 
Z = (13-18)/1 = -5.0 
p < .0000 
Reject Ho 
ViSta Applet
 
Sample Mean = 16.5 
Z = (16.5-18)/1 = -1.5 
p = .1339 
Do Not Reject Ho 
ViSta Applet
 
ViSta's Report for Univariate Analysis of Experiment 1 Data. 
ViSta's Report for Univariate Analysis of Experiment 1 Data. 
3. Directional (One-Tailed) Hypothesis Testing
What we have seen so far is called non-direction, or 
"Two-Tailed"
, hypothesis testing. 
Its called this because the critical region is in both tails of the distribution. It is used when 
the experimenter expects a change, but doesn't know which direction it will be in.
(a). Non-directional (Two-Tailed) Hypothesis
The statistical hypotheses (Ho and H1) specify a change in the population mean score.
In this section we can consider directional, 
"One-Tailed"
, hypothesis testing. This is 
what is used when the experimenter expects a change in a specified direction.
(b). Directional (One-Tailed) Hypothesis
The statistical hypotheses (Ho and H1) specify either an increase or a decrease in the 
population mean score.

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Example:
We return to the survey data that we obtained on the first day of class. Recall 
that our sample has n=41 students.
Sample Statistics, Population Parameters