Answer:
Critical value can be reduced by decreasing confidence levels, for eg, 95% critical value < 99% like that
Or sample size can be increased suitably.
Explanation:
The question is the methods that can be used to decrease the margin of error.
For understanding we must understand first how margin of error is calculated
Margin of error = Critical value of test statistic * std deviation/square root of sample size
Thus we find if we want to decrease the margin of error,
Either critical value should be reduced or
Sample size should be increased.
Or std deviation should be reduced.
Critical value can be reduced by decreasing confidence levels, for eg, 95% critical value < 99% like that
Or sample size can be increased suitably.
Normally std deviation cannot be altered for a given sample hence the above two only work out.