A Critique of the Proposed National Education Policy Reform
Research hypothesis
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14. A nondirectional alternative hypothesis states that the null
hypothesis is wrong. A nondirectional alternative hypothesis
does not predict whether the parameter of interest is larger or
smaller than the reference value specified in the null
hypothesis.
A directional alternative hypothesis states that the null
hypothesis is wrong, and also specifies whether the true
value of the parameter is greater than or less than the
reference value specified in null hypothesis.
The advantage of using a directional hypothesis is increased
power to detect the specific effect you are interested in. The
disadvantage is that there is no power to detect an effect in
the opposite direction.
15. Example of directional and nondirectional hypotheses
Nondirectional
A researcher has results for a sample of students who took a
national exam at a high school. The researcher wants to know if
the scores at that school differ from the national average of 850.
A nondirectional alternative hypothesis is appropriate because
the researcher is interested in determining whether the scores
are either less than or greater than the national average. (H0: μ =
850 vs. H1: μ≠ 850)
Directional
A researcher has exam results for a sample of students who took
a training course for a national exam. The researcher wants to
know if trained students score above the national average of
850. A directional alternative hypothesis can be used because
the researcher is specifically hypothesizing that scores for trained
students are greater than the national average. (H0: μ = 850 vs.
H1: μ > 850)
16. Activity
Change the following questions into hypothesis using the
If...then format.
1. How does the amount of daylight affect the number of
eggs laid by a chicken?
2. How does classroom temperature affect students'
performance in a test?
3.How will batting practice affect a players' batting
average?
4. How does advertising affect the sales of Orbit White?
5. Does adding fertilizer affect the growth of a plant?
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45. Name: ____________________________
For each item below, specify the independent and dependent variables, as well as constants.
1. A study was done to find if different tire treads affect the braking distance of a car.
I: _________________ D: ___________________ C: __________________
2. The time it takes to run a mile depends on the person’s running speed.
I: ________________ D: ___________________ C: __________________
3. The height of bean plants depends on the amount of water they receive.
I: ________________ D: ___________________ C: __________________
4. The higher the temperature of the air in the oven, the faster a cake will bake.
I: ________________ D: ___________________ C: __________________
5. Lemon trees receiving the most water produced the most lemons.
I: ________________ D: ___________________ C: __________________
6. An investigation found that more bushels of potatoes were produced when the soil was
fertilized more.
I: ________________ D: ___________________ C: __________________
7. Students measured the temperature of the water at different depths in Lake Skywalker and
found that the temperature varied.
I: ________________ D: ___________________ C: __________________
8. The amount of pollution produced by cars was measured for cars using gasoline containing
different amounts of lead.
I: ________________ D: ___________________ C: __________________
9. Four groups of rats are first massed and then fed identical diets except for the amount of
vitamin A they receive. Each group gets a different amount. After 3 weeks on the diet, the rats’
masses are measured again to see if there has been a decrease.
I: ________________ D: ___________________ C: __________________
