StatisticsPractice Questions & MCQs

Q1. If for a grouped data Σf_i u_i = 25, Σf_i = 50, a = 70 and h = 4, what is the mean?

• A.72
• B.75
• C.70.5
• D.68

Answer: A. 72

We are told: 25; 50; 70; 4. To find: what is the mean?. Key equation - Mean = a + h · (Σfu / Σf) = 70 + 4·(25/50) = 70 + 2 = 72. This is the equation that links the given quantities to the unknown (math, chapter 'Statistics'). Step-by-step: Mean = a + h · (Σfu / Σf) = 70 + 4·(25/50) = 70 + 2 = 72. Consequently the answer is A) 72.

Q2. If the sum of deviations from the mean of 30 observations is computed about 25 and equals 60, what is the mean?

• A.27
• B.30
• C.25.6
• D.28

Answer: A. 27

Given 30, 25, 60, asked for computed about 25 and equals 60, what is the mean?. By Σ(x_i − 25) = 60 ⇒ Σx_i = 30·25 + 60 = 810. Σ(x_i − 25) = 60 ⇒ Σx_i = 30·25 + 60 = 810 → Mean = 810/30 = 27. So option A) 27.

Q3. The mean of a set of 25 observations is 18.2. If two observations 12 and 22 are removed, what is the mean of the remaining?

• A.18.30
• B.17.95
• C.18.5
• D.19.0

Answer: A. 18.30