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The use of the interval p ± ( z critical value) requires a large sample. For eac

ID: 3135260 • Letter: T

Question

The use of the interval

p ± (z critical value)

requires a large sample. For each of the following combinations of n and p, indicate whether the sample size is large enough for use of this interval to be appropriate.

(a)    n = 50 and p = 0.30

YesNo    


(b)    n = 50 and p = 0.05

YesNo    


(c)    n = 15 and p = 0.45

YesNo    


(d)    n = 101 and p = 0.03

YesNo    


(e)    n = 101 and p = 0.80

YesNo    


(f)    n = 50 and p = 0.2

YesNo    


(g)    n = 60 and p = 0.2

YesNo    


(h)    n = 81 and p = 0.10

YesNo   

p(1 p) n

Explanation / Answer

The confidence interval calculations for the proportion is dependent on the following assumptions: both np 10 and n(1-p) 10.

(a)np^=50*0.30=15>10, n(1-p^)=50*0.70=35>10

Yes, the sample size is large enough for use of this interval to be appropriate.

(b) np^=50*0.05=2.5<10, n(1-p^)=50*0.95=47.5>10

No, the sample size is large enough for use of this interval to be appropriate.

(c) np^=15*0.45=6.75<10, n(1-p^)=15*0.45=8.25<10

No, the sample size is large enough for use of this interval to be appropriate.

(d) np^=101*0.03=3.03<10, n(1-p^)=101*0.97=97.97>10

No, the sample size is large enough for use of this interval to be appropriate.

(e) np^=101*0.80=80.8>10, n(1-p^)=101*0.20=20.2>10

Yes, the sample size is large enough for use of this interval to be appropriate.