Work Sampling Techniques and Applications

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Questions and Answers

What is the key concept behind work sampling?

Using a stopwatch to measure the duration of tasks performed by workers.

Randomly selecting a small group of workers to represent the entire workforce.

Observing and analyzing the time spent on different activities in a process. (correct)

Measuring the output of workers over a period of time.

What did L. Tippet initially use work sampling for in 1927?

Evaluating the performance of workers in a cotton industry. (correct)

Analyzing the productivity of textile mills.

Studying the efficiency of manufacturing processes.

Assessing the effectiveness of different work methods.

What does the term 'confidence level' refer to in work sampling?

The degree of certainty about the results obtained from the sample. (correct)

The level of agreement among researchers about the study's findings.

The accuracy of the sample data collected in a study.

The probability of achieving a specific target in a work process.

What is the role of the normal distribution curve in work sampling?

To visualize the probability of occurrence of certain events in a work process. (A) Signup and view all the answers

What is the relationship between the sample size and the margin of error in work sampling?

Larger sample size leads to a smaller margin of error. (D) Signup and view all the answers

What is the primary objective of Work Sampling, based on the provided text?

To analyze the efficiency of a work process by observing the working and idle times. (D) Signup and view all the answers

What is the underlying concept or theory behind Work Sampling as stated in the text?

The percentage of observed occurrences in a state reflects the actual proportion of time spent in that state. (C) Signup and view all the answers

What are the three primary applications of Work Sampling according to the text?

Ratio study, performance sampling, and work measurement. (D) Signup and view all the answers

What is the significance of the phrase 'sufficient number of observations' in the context of Work Sampling?

It ensures that the observations are representative of the overall process. (A) Signup and view all the answers

What key element is emphasized in the text as critical for the accuracy of Work Sampling?

The randomness of the observations. (E) Signup and view all the answers

Which of the following is NOT explicitly mentioned as a possible state of a machine or a worker in the provided text?

Repair (A) Signup and view all the answers

What is the difference between a ratio study and a performance sampling study in the context of Work Sampling?

A ratio study analyzes the proportions of working and idle times, while a performance sampling study measures the performance of specific tasks against a standard. (C) Signup and view all the answers

What is the best way to ensure that the observations in Work Sampling are random?

Using a random number generator to select both observation times and points. (C) Signup and view all the answers

In the initial example, what is the confidence level used for the analyst's estimation?

99% (D) Signup and view all the answers

What is the formula used to calculate the number of observations needed for the activity estimation?

$N = \frac{z^2p(1-p)}{e^2}$ (B) Signup and view all the answers

What is the margin of error used for the estimation of the activity?

5% (A) Signup and view all the answers

What is the value of 'z' used to calculate the number of observations in the first scenario?

2.326 (A) Signup and view all the answers

In the second scenario, what is the percentage of time the machine is idle?

20% (C) Signup and view all the answers

What is the limit error percentage in the second scenario?

9.55% (C) Signup and view all the answers

What is the z-value obtained for the second scenario?

2.327 (D) Signup and view all the answers

What is the formula used to calculate the z-value in the second scenario?

$Z = \frac{e \sqrt{n}}{\sqrt{p(1-p)}}$ (C) Signup and view all the answers

What does the variable 'n' represent in the equation provided?

The sample size desired for the accurate study (B) Signup and view all the answers

If the preliminary study has 10 readings, and the sum of the readings is 50, what is the value of (∑𝑥)2?

2500 (C) Signup and view all the answers

In the provided equation, what is the purpose of the term "√n' ∑𝑥2 - (∑𝑥)2"?

To measure the overall variability of the readings (A) Signup and view all the answers

If the sum of the squared values of the readings (∑𝑥2) is 150 and the sum of the readings (∑𝑥) is 30, what is the value of "√n' ∑𝑥2 - (∑𝑥)2" when n'= 5?

√600 (B) Signup and view all the answers

What is the purpose of the equation provided in the context of time study analysis?

To estimate the number of readings needed for an accurate time study (C) Signup and view all the answers

Why is it necessary to increase the sample size when the calculated sample size ('n') is greater than the number of preliminary readings ('n')?

To increase the precision of the time study (A) Signup and view all the answers

If the analyst determines that the accurate sample size ('n') is 12, and the preliminary study only had 8 readings, what should the analyst do?

Continue taking readings until the sample size reaches 12 (C) Signup and view all the answers

What is the primary advantage of using this equation to determine the sample size?

It ensures that the sample size is large enough to be reliable (A) Signup and view all the answers

What is the total number of observations made during this work sampling study?

825 (A) Signup and view all the answers

What percentage of the employee's time was spent on personal time?

9.2% (D) Signup and view all the answers

What is the proportion of observations used to calculate the idle time percentage?

207/828 (C) Signup and view all the answers

In the formula provided, what does 'P' represent?

The proportion of observations for a specific activity (B) Signup and view all the answers

What is the value of 'Z' in the formula provided, given a confidence level of +-3.5% and the proportion of idle time 'P' = 207/828?

2.17 (D) Signup and view all the answers

Given a confidence level of +-3.5% and an idle time proportion of 207/828, how many observations would be required for the study?

500 (B) Signup and view all the answers

If the branch manager wanted to increase the confidence level of the study to +-5%, how would this impact the required number of observations?

The required number of observations would increase. (D) Signup and view all the answers

Based on the provided information, what is the estimated percentage of time spent on 'Meeting with welfare client'?

56.3% (D) Signup and view all the answers

What is the formula used to determine the required number of readings 'n' for an accurate work sampling study?

n = (40 * √(n' * ∑x² - (∑x)²)) / ∑x (D) Signup and view all the answers

What is the value obtained for 'n' from the example provided in the content?

9 (D) Signup and view all the answers

What action should the analyst take if the calculated value for 'n' is greater than the initial sample size?

Increase the sample size to match the calculated value. (A) Signup and view all the answers

Based on the content, what does 'n' represent in the formula?

The required sample size for an accurate study (D) Signup and view all the answers

In the example provided, what is the calculated value for 'n'?

8.81 (A) Signup and view all the answers

In the provided example, what is the value of the summation of all time readings (∑x)?

77.39 (B) Signup and view all the answers

In the formula, what does 'n'' represent?

The initial sample size (B) Signup and view all the answers

What is the purpose of the formula used to determine 'n'?

To determine the most appropriate sample size for the study (C) Signup and view all the answers

Study Notes

Work Sampling

Work sampling is a method used to find the percentage of time a specific activity occurs.
It involves making a large number of instantaneous observations at random intervals over a period of time.
Each observation records the activity occurring at that specific time.
The percentage of observations for each activity is recorded.

Scope of Study

Before observations, the objective of the work sampling must be determined.
The simplest objective is to determine if a machine or worker is idle or working.
This is measured to determine the time a machine is idle or working.

Work Sampling Categories

Ratio study of working and idle times
Performance sampling study, measuring working and idle times to create a performance index
Work measurement technique

Theory of Work Sampling

The percentage of observations recorded for an activity is a good estimate of the actual time spent on that activity.
Random observations and a sufficient number of observations are crucial for accurate results.
The error in this technique decreases as the number of samples increases.

Confidence Levels

Confidence levels and normal distribution curves are essential for representing the probability of change of occurrence.
The area under the curve within 1 standard deviation of the mean equals 68%.
The area under the curve within 2 standard deviations of the mean equals 95%.
The area under the curve within 3 standard deviations of the mean equals 99.7%.
Confidence levels of 90%, 95%, 99%, and 99.9% are commonly used.

Margin of Error

Margin of error is a statistic representing the amount of random sampling error in survey results.
A larger margin of error means less confidence in the poll's results.
Margin of error is often used in scenarios where a population isn't completely surveyed and to report observational error.

Sample Size Determination

A statistical method or conventional method can be used to determine the sample size needed.
A preliminary study, giving a number of readings, is required using a particular formula to obtain a sample size.

Example Problems

Problems are provided for various scenarios, involving different values and conditions.
Examples show how to calculate the needed number of observations depending on the confidence level and error limit.
Examples illustrate the calculation process.

Work Sampling in Bracelet Assembly

A Bead String Company case study is presented.
The case details the process of making a bracelet with beads and string and the steps involved.
The time study aims to determine the time for each step.

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Description

This quiz covers the principles and methods of work sampling, including how to measure the percentage of time specific activities occur. It explores the objectives, categories, and the theoretical basis of work sampling. Test your understanding of this essential performance measurement technique!