Question on Range Estimates

Could you please answer the below question and justify your answer?

Assuming that the ends of a range estimates are +/-3 Sigma from the mean, which of the following range estimates involves the LEAST risk?

a. 30 days, plus or minus five days
b. 22 - 30 days
c. Optimistic = 26 days, most likey = 30 days, pessimistic = 33 days
d. Mean of 28 days
 
 

 Appreciate your response and apolize if this question is dumb.

I believed answer C since another name of sigma is deviation. Answer C can use to calculate the range with can use for 3 sigma.

 

Any one have better answer ?

the answer is C because it is dependent on how small is the range.

a) range of 10 days since 30 days +/- 5 days = 25 to 35 days

b) range of 8 days since difference between 22 and 30 is 8.

c) range of 7 days since difference between 26 and 33 = 7

d) Mean of 28 days does not give a range.

smallest range is the least risky range and please note that +/-3 sigma is irrelavant.

 

 Thank you ahujar