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Chapter 6: Q. 50 (page 389)

Typographical and spelling errors can be either “nonword errors” or “word errors.” A nonword error is not a real word, as when “the” is typed as “teh.” A word error is a real word, but not the right word, as when “lose” is typed as “loose.” When students are asked to write a 250-word essay (without spell-checking), the number of nonword errors X in a randomly selected essay has mean 2.1 and standard deviation 1.136. The number of word errors Y in the essay has mean 1.0 and standard deviation 1.0. Calculate and interpret the mean of the sum S = X + Y.

Short Answer

Expert verified

The Average mean value isμ=3.1

Step by step solution

01

Given information

The number of nonword errors X in a randomly selected essay has mean 2.1 and standard deviation 1.136

The number of word errors X in a randomly selected essay has mean 1.0 and standard deviation 1.0

μX=2.1σX=1.136μY=1.0σY=1.0

X = quantity of nonword errors in an essay chosen at random

Y= quantity of word errors in an essay chosen at random

02

Calculations

μ=μX+μY=2.1+1.0=3.1

There are two different random variables with two different means,μX=2.1and μY=1.0

as a result, the average of the two random numbers ,the total of their means will be the variable.

On average, there will be a total number of 3.1 errors

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