Retired Moderator
Joined: 16 Apr 2020
Status:Founder & Quant Trainer
Affiliations: Prepster Education
Posts: 1546
Given Kudos: 172
Location: India
WE:Education (Education)
Re: The U.S. Weather Bureau has provided the following informati
[#permalink]
20 Aug 2021, 02:09
Explanation:
To find the mean, let us first arrange these 20 terms in ascending order:
464, 505, 564, 585, 604, 608, 616, 653, 657, 660, 697, 704, 741, 856, 888, 906, 918, 926, 947, 1102
Median (for even number of terms) = \(\frac{10^{th} term + 11^{th} term}{2} = \frac{660 + 697}{2} = 678.5\)
Average (given) = 730
SD (given) = 168
1SD of mean means 1SD above or 1SD below mean i.e. (730 - 168) to (730 + 168) = 562 to 898
Find the numbers which are less than the median;
464, 505, 564, 585, 604, 608, 616, 653, 657, 660
Which are not within one standard deviation of the mean;
464, 505, 564, 585, 604, 608, 616, 653, 657, 660
Required probability = \(\frac{2}{20} (100) = 10\)%
Hence, option A