Work Sampling Techniques and Applications

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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?

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

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

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

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

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

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

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

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

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

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

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

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

<p>The randomness of the observations. (E)</p> 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?

<p>Repair (A)</p> 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?

<p>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)</p> Signup and view all the answers

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

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

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

<p>99% (D)</p> Signup and view all the answers

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

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

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

<p>5% (A)</p> Signup and view all the answers

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

<p>2.326 (A)</p> Signup and view all the answers

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

<p>20% (C)</p> Signup and view all the answers

What is the limit error percentage in the second scenario?

<p>9.55% (C)</p> Signup and view all the answers

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

<p>2.327 (D)</p> Signup and view all the answers

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

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

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

<p>The sample size desired for the accurate study (B)</p> 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?

<p>2500 (C)</p> Signup and view all the answers

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

<p>To measure the overall variability of the readings (A)</p> 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?

<p>√600 (B)</p> Signup and view all the answers

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

<p>To estimate the number of readings needed for an accurate time study (C)</p> 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')?

<p>To increase the precision of the time study (A)</p> 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?

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

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

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

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

<p>825 (A)</p> Signup and view all the answers

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

<p>9.2% (D)</p> Signup and view all the answers

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

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

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

<p>The proportion of observations for a specific activity (B)</p> 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?

<p>2.17 (D)</p> 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?

<p>500 (B)</p> 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?

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

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

<p>56.3% (D)</p> 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?

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

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

<p>9 (D)</p> 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?

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

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

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

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

<p>8.81 (A)</p> Signup and view all the answers

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

<p>77.39 (B)</p> Signup and view all the answers

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

<p>The initial sample size (B)</p> Signup and view all the answers

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

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

Flashcards

Work Sampling

A method for determining the percentage of time an activity occurs through random observations.

Instantaneous Observations

Observations made at random time intervals to capture activity status.

Idle Time

Duration when a machine or worker is not engaged in productive activity.

Performance Index

A prepared index based on the comparison of working and idleness times.

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Random Observations

Observations taken at no fixed intervals to ensure unbiased data collection.

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Objective of Work Sampling

The goal of determining whether machines or workers are idle or working.

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Reliability of Observations

The accuracy of estimating activity states based on a sufficient number of random observations.

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Work Measurement Technique

The use of work sampling as a method to assess productivity.

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Sampling

The process of obtaining a sample for research.

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Sample

A group in a study from which information is gathered.

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Probability

The extent to which an event is likely to occur.

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Normal Distribution Curve

Graphical representation of the probability of occurrences in work sampling.

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Margin of Error

The range of values within which the true value is expected to fall.

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Confidence Level

The probability that the sample accurately reflects the population.

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Observational Requirement Formula

A formula used to calculate the required number of observations needed.

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Z-score

A statistical measurement that describes a value's relation to the mean of a group of values.

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Running Time

The percentage of time a machine or worker is actively working.

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Idle Probability

The likelihood that a machine is not engaged in productive activity during observation.

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Sample Size Calculation

The process of determining the number of observations needed for accurate results.

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Idle Time Percentage

The proportion of time a worker is not engaged in work activities.

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Formula for Idle Time

Idle Time = (Idle Observations / Total Observations) x 100.

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Error Margin in Sampling

The allowable deviation from the estimated value, expressed in percentage.

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Sample Size (n) Calculation

Determining how many observations should be made to ensure reliability.

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Total Observations (n)

Sum of all individual observations counted in a study.

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P in Sampling Formula

The proportion of interest, often the fraction of events occurring.

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Z Value in Statistics

A constant that reflects the number of standard deviations from the mean.

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Sample Size (n)

The number of observations or readings needed for a study.

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Preliminary Study

An initial phase where data readings are taken to estimate sample size.

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Sum of Values (Σx)

The total of all observations or readings taken.

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Square of the Values (Σx²)

The sum of the squares of each individual reading.

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Equation Purpose

To calculate the required sample size based on preliminary data.

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Adjusting Sample Size

Increasing the number of readings based on preliminary analysis.

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Calculation Example

A numerical illustration of the sample size calculation.

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Required Readings

The final number of observations needed for an accurate study.

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Preliminary Readings

Initial observations made before determining the final sample size.

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Total Reading Sum (∑x)

The sum of individual readings, crucial for calculations.

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Readings Required

The necessary number of observations to achieve a valid result.

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Squared Reading Sum (∑x^2)

The sum of the squares of each individual reading.

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Formula for Sample Size (n)

Mathematical expression used to calculate required readings.

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Observation Cycle

A set of readings taken in a sequence during the study.

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Time Study Analysis

The assessment of time taken for tasks to determine efficiency.

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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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Lesson 4 - Work Sampling PDF

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