1aWhat does the null hypothesis predict about a population or a treatment effect
ID: 3174691 • Letter: 1
Question
1aWhat does the null hypothesis predict about a population or a treatment effect? What does the alternative hypothesis predict? b.As the alpha level gets smaller, the size of the critical region also gets smaller. True or false? c. A decision to reject the null hypothesis indicates that the treatment has no effect. True or false? d. What is the advantage of using a one-tailed test when your theory predicts a particular direction of result? Why might you use a two-tailed test even when your theory predicts a particular direction of result? e. A researcher predicts that a treatment will lower scores. If this researcher uses a one-tailed test, will the critical region be in the right or left tail of the distribution? f. How is a Z test different from a Z score?
Explanation / Answer
Answer to part a)
The null hypothesis predicts that the treatment is not effective, and that the population behaves same as without treatment
Alternate hypothesis: predicts or concludes that the treatment has a significant effect , and that the treatment is highly effective on the population.
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Answer to part b)
It is true, as the value of alpha that is the significance level increases, the critical region reduces.
Say for Alpha = 0.05 , Z = 1.645, critical region is area to the right of it
For alpha = 0.01 , Z = 2.33 , the critical region is to its right side.
Thus we can see as the value of alpha decreased, the critical region also decreased.
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Answer to part c)
The main aim of hypothesis testing is to reject the null and conclude that the alternate hypothesis is correct. Thus if we reject the null hypothesis, this would be indicate that the effect is statistically signficant. Thus the statement we got : that if we reject the null this would mean that there is no effect is false
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Answer to part d)
When we already know the direction , it is better to apply one-tailed test , because we already know that the critical region would fall in a particular direction only, Applying a two tailed test instead will cross verify the chance of the critical region lying on the other side as well. generally two tailed test is applied when we want to test the parameter for a specific value, in that case either a higher or a lower value creates a difference & would be important to identify.
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Answer to part e)
When the claim of the researcher is that the treatment will lower the scores, a left tailed test must apply. This is because the null would be that the score is equal or greater , and the alternate hypothesis would be that the score would be lower. Thus the critical region lies under the left tail.
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Answer to part f)
The Z score is merely a standardized number that shows how far a raw score is ffrom the mean , and the difference is expressed in terms of standard deviation.
whereas in a Z test, the vlaue to be tested is converted to a Z score and then the probability or p value is calculated to evalaute whether there are chances of the null to be accepted or not.
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