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Calculating sample size for Continuous Data

How to Calculate Sample Size for Continuous Data: A Simple Guide

To estimate the sample size for continuous data, one can use a simple algorithm. Let us overview the following steps by breaking them down:

1: Estimate the Standard Deviation: First, find the standard deviation. One can obtain it, by finding a range – the difference between the maximum and minimum values – and dividing by 5.

2: Determine Required Precision: After that, determine the desired precision level to find the accuracy of the estimate.

3: Calculate the Minimum Sample Size: With standard deviation and precision in hand, find the minimal sample as follows: 

MSS = ((2 x standard deviation  / precision)²

For example, if the completion of an entire process ranges from 10 to 30 days,

  • The standard deviation is 30 – 10 / 5 = 4 days.
  • If my accuracy level required is ±2 days, then MSS = ((2 x 4)/2)²=16

Always note that the level of accuracy influences the number of measurements. Meaning, one is forced to adjust the number of measurements up once between 1000 and 2000.

Thus, using the above method, you can easily arrive at the actual figure needed to measure.

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