Confidence level

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MCQ 129

Q1. When the confidence level of a test is increased which of the following will happen

a) No effect on significance

b) Previously insignificant value becomes significant

c) Previously significant value becomes insignificant

d) No change in hypothesis

ANSWER:

Ans : C
If we increase the CI limit , the level of significance i.e. LOS=100-CI will be less. In other words by increasing the CI we decrease the probability of rejecting null hypothesis by chance. So, if at 95% CI, the LOS was 5% or 0.05, so value of 0.04 will be significant but if we say at 99% CI, the LOS will be 1% or 0.01 so p value less than 0.01 will be significant only. So we can say that by increasing the CI, previously significant difference will become non significant.

MCQ 130

Q2. When the confidence limit of a test is decreased which of the following will happen 

a) No effect on significance

b) Type I error will occur

c) Previously significant value becomes insignificant

d) No change in hypothesis

ANSWER:

Answere here is : B - Type I error will occur.
The area between two CI limit is Zone of acceptance of Null hypothesis ( Not significant result), and outside this limit is zone of rejection of null hypothesis ( Significant result). So, if we decrease the CI, the observation which was plotted in Zone of acceptance gets shifted to zone of rejection i.e. not significant results become significant.

Thus Option C is correct when the confidence limit is Increased.

Type I error is Rejection of Null hypothesis despite of it being true. It’s a very dangerous error and occurs if we decrease the CI limit.

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