A researeher wants to conduct a before/after study on 11 subjects to determine i

Question

A researeher wants to conduct a before/after study on 11 subjects to determine if a new cholesterol medication results in higher HDL cholesterol readings. The null hypothesis is that the average difference is zero while the alternative hypothesis is that the average difference is not zero. Scores are obtained on the subjects both before and after taking the medication. After subtracting the after scores from the before scores, the average difference is computed to be -2.40 with a sample standard deviation of 1.21. A 0.05 level of significance is selected. The degrees of freedom for this test are. 11 10 9 20 2 The observed t value for this test is. -21.82 -6.58 -2.4 1.98 2.33 The table t value for this test is. 1.812 2.228 2.086 2.262 3.2467 Shall we reject the Null Hypothesis? Yes No

Explanation / Answer

21.

Here,

df = n - 1 = 11 - 1 = 10 [ANSWER, B]

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22.

Formulating the null and alternative hypotheses,              
              
Ho:   ud   =   0  
Ha:    ud   =/   0  
              
As we can see, this is a    two   tailed test.  
Getting the test statistic, as              
              
X = sample mean =    -2.4          
uo = hypothesized mean =    0          
n = sample size =    11          
s = standard deviation =    1.21          
              
Thus, t = (X - uo) * sqrt(n) / s =    -6.578429336 = -6.58 [ANSWER, B]

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23.  
                  
Thus, getting the critical t,              
df = n - 1 =    10          

So at 0.05, two tailed,

tcrit =    +/-   2.228 [ANSWER, B]

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24. As |t| > 2.228, we reject Ho. [ANSWER: YES]

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