iv)  Calculate the proportion of spacers produced that have a length within 0.5 mm of the population mean. v)  Find the length that 90% of spacers will exceed

Glencoe Algebra 1, Student Edition, 9780079039897, 0079039898, 2018
18th Edition
ISBN:9780079039897
Author:Carter
Publisher:Carter
Chapter10: Statistics
Section10.4: Distributions Of Data
Problem 19PFA
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I need help with the last two questions IV & V at the bottom of the page, i have included the other working out to help

  1. a)  A company produces metal spacers that are placed between bars in the construction of a range of high precision prefabricated metal items. The spacers are produced so that the length of each is normally distributed with a mean of 40 mm and a standard deviation of 1.5 mm. The spacers are then packaged into groups of 4 for sale. Note: You may use Excel functions to answer the following questions for all parts ii, iii, iv and v and also b. part ii you must provide logical working that includes the Excel function, the Excel output and an appropriate diagram.
  1. i)  If X is the random variable representing the length of a single spacer, then identify the type of distribution the random variable has and write down the value(s) of the parameter(s) of this distribution.

 

1.(i) The distribution of X is Normal distribution.

The parameters are 

Mean, μ = 40

Standard deviation, σ = 1.5

 

  1. ii)  Determine the probability that a randomly selected spacer has a length less than 37.75 mm.

2.(ii).

P( X < 37.75 )

 = P[( X - μ )/σ < (37.75 - 40)/1.5]

  = P( Z < -1.5 )

  = 0.06681

 Note: The Excel command for getting the p-value of P( Z < -1.5 )

=NORM.S.DIST(-1.5,TRUE

  1. iii)  Calculate the proportion of spacers produced with length greater than 43.75mm.

3.(iii):

P( X > 43.75 )

 = P[( X - μ )/σ > (43.75 - 40)/1.5]

  = P( Z > 2.5 )

  = 0.00621

 Note: The Excel command for getting the p-value of P( Z > 2.5 )

=1-NORM.S.DIST(2.5,TRUE)

 

  1. iv)  Calculate the proportion of spacers produced that have a length within 0.5 mm of the population mean.
  2. v)  Find the length that 90% of spacers will exceed

 

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