Page 89 - Math SL HB Sem 3

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(Question continued)

Consider the class interval 45 <T < 55 .

(c) (i) Write down the interval width.

(ii) Write down the mid-interval value- marks]
[2

(d) Hence find an estimate for the

(i) mean;

(iD standarddeviation. marks]
[4

John assumes that I is normally distributed and uses this to estimate the probability
that a child takes less than 95 seconds to solve the puzzle.

(e) Find John's estimate.
[2 marksJ

-4- SPEC/5/IVIATMF/SP2EN GIZ|lxx
[Maxinun nark: 6J
iP

A random variable X is distributed normally with mean 450. It is known that
P(X>a)=a)t.

(a) Reprcsent all this information on the following diagram_
p narksl

(b) Given that the standard deviation is 20, find a. Give your answer corect to the
nearest whole number,
P narksl

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