18 b.  What is the null hypothesis?    c. What is the value of  t obtained.  d. What is the value of t-critical α = 0.05 1 tail.    d. What might the candidate conclude using  α = 0.05 1  tail?  e. What type error might the candidate have made?  f.  Estimate the size of the real effect using omega squared and cohen’s d.  Is the effect a large one?     ώ2 = tobt2 -1                                     tobt2 +N-1   ώ2 =   Cohen’s d Estimated d = Xbar1-Xbar2                            Spooled   Spooled=the square root of the pooled variance   sp2= SS1+SS2   =                n1+n2-2

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2. A nurse was hired by a governmental ecology agency to investigate the impact of a lead smelter on the level of lead in the blood of children living near the smelter. Ten children were chosen at random from those living near the smelter. A comparison group of seven children was randomly selected from those living in an area relatively free from possible lead pollution. Blood samples were taken from the children and lead levels determined. The following are the results (scores are in micrograms of lead per 100 milliliters of blood.

                                                           Lead Levels

Children living near smelter                                  Children living in unpolluted area

18                                                                              9

16                                                                              13

21                                                                              8

14                                                                              15

17                                                                              17

19                                                                              12

22                                                                              11

24

15

18

b.  What is the null hypothesis? 

 

c. What is the value of  t obtained. 

d. What is the value of t-critical α = 0.05 1 tail.   

d. What might the candidate conclude using  α = 0.05 1  tail

e. What type error might the candidate have made? 

f.  Estimate the size of the real effect using omega squared and cohen’s d.  Is the effect a large one?

 

 

ώ2 = tobt2 -1                           

         tobt2 +N-1

 

ώ2 =

 

Cohen’s d

Estimated d = Xbar1-Xbar2

                           Spooled

 

Spooled=the square root of the pooled variance

 

sp2= SS1+SS2   =      

         n1+n2-2                                

 

 

 

 

 

 

Estimated d = 

                           

 

 

 

 

g. Do you satisfy the assumption of homogeneity of variance?How do you know?

 

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