Stats Homework quetions

Question 1

A manufacturer of hand made desks made for the last few years 10 .1 averages ) per day with a 3 .5 desk Standard deviation . s are exceeding the production , so the process was studied , some potential solutions were discussed , and the easiest one was implemented . A study was undertaken to asses the production rate . Randomly sampling 30 (n days of production , the sample mean was 12 .2 (Xbar ) desks . Run a hypothesis test

One Tail Z , with the alpha at 0 .01 to determine if the production rate went

up statistically

Solution and Sample size n 30 At 0 .01 zcritical t0 .01 ,29 2 .46

Decision Rule : Reject Ho if zcalculated zcritical As , zcalculated zcritical , therefore Null Hypothesis is rejected and alternate hypothesis is accepted . In other words the production rate has gone up statistically

Question 2

This is a Z hypothesis test to determine if a training program I developed had any statistical value or not

We are measuring the time it takes to get a job done . We believed after some

Strategizing that some practices were not up to speed so we re-trained

Some of the people and then gave them the same jobs as before to see if

Their time altered STATISTICALLY Of course it did mathematically

Looking at the problem below , historically they used to AVERAGE 13 .8 (Population mean

Hours and the test returned a sample mean of 12 .2

We will run a 1 tail Z hypothesis test with an alpha of 0 .05 and see if the training and procedure rewrite helped

Now , you , if you use step 3 correctly will get a minus sign for Zcalc

In this class the - sign is not algebraic . All it means is the sample mean (12 .2 ) is less in value than the population mean (13 .8 . These tests are absolute valued tests . You will not find any negative signs in any of the tables we will use . Use the Student 's t table to find Zcrit My lecture describes how to find the critical value for a Z test

Over the last year where I work , we measured the average time it took to remove /replace an engine and transmission from one type of bus we have in the fleet . The historical average was 13 .8 hours with a 2 .9 hour standard deviation . We researched the procedures , rewrote them and randomly trained a sample group of mechanics . For 32 random jobs , we tracked the time and came up with a 12 .2 hour sample average

Run a 1 tail Z hypothesis test with an alpha of 0 .05 and see if the training and procedure rewrite helped

Solution

and Sample Size n 32 At 0 .05 zcritical - t0 .05 ,31 -1 .7

Decision Rule : Reject Ho if zcalculated zcritical AS , zcalculated zcritical , therefore Null Hypothesis is rejected and alternate hypothesis is accepted . In other words the the training and procedure rewrite helped in reducing the time to remove /replace engine and...