JAMB Mathematics Past Questions & Answers - Page 279

1,391.

Let p be a probability function on set S, where S = (a1, a2, a3, a4). Find P(a1) if P(a2) = \(\frac{1}{3}\), p(a3) = \(\frac{1}{6}\) and p(a4) = \(\frac{1}{5}\)

A.

\(\frac{7}{3}\)

B.

\(\frac{2}{3}\)

C.

\(\frac{1}{3}\)

D.

\(\frac{3}{10}\)

Correct answer is D

No explanation has been provided for this answer.

1,394.

The variance of the scores 1, 2, 3, 4, 5 is

A.

1, 2

B.

1, 4

C.

2.0

D.

3.0

Correct answer is C

\(x\) 1 2 3 4 5 sum =15
\(x - \bar{x}\) -2 -1 0 1 2  
\((x - \bar{x})^{2}\) 4 1 0 1 4 10

Mean = \(\frac{15}{5} = 3\)

\(Variance = \frac{\sum (x - \bar{x})^{2}}{n}\)

= \(\frac{10}{5}\)

= \(2.0\)

 

1,395.

\(\begin{array}{c|c} class& 1 - 3 & 4 - 6 & 7 - 9\\ \hline Frequency & 5 & 8 & 5\end{array}\)
Find the standard deviation of the data using the table above

A.

5

B.

\(\sqrt{6}\)

C.

\(\frac{5}{3}\)

D.

\(\sqrt{5}\)

Correct answer is D

\(\begin{array}{c|c} \text{class intervals} & Fre(F) & \text{class-marks(x)} & Fx & (x - x)& (x - x)^2 & F(x - x)^2 \\ \hline 1 - 3 & 5 & 2 & 10 & -3 & 9 & 45\\ 4 - 6 & 8 & 5 & 40 & 0 & 0 & 0 \\ 7 - 9 & 5 & 8 & 40 & 3 & 9 & 45 \\ \hline & 18 & & 90 & & & 90 \end{array}\)

x = \(\frac{\sum fx}{\sum f}\)

= \(\frac{90}{18}\)

= 5

S.D = \(\frac{\sum f(x - x)^2}{\sum f}\)

= \(\frac{90}{18}\)

= \(\sqrt{5}\)