Collected and classified figures are vast. To condense these figures we use average. Average converts the whole set of figures into just one figure and thus helps in condensation. In this case, the formula is calculating the mean by summing all of the observations and dividing by the number of observations.
There is some notation that you will come to see as standards, i. We will make a point of letting you know what these are. However, when it comes to the variables, these labels can and do vary.
The most important step in finding the median is to first order the data from smallest to largest. If the sample size is an odd number then the location point will produce a median that is an observed value.
If the sample size is an even number, then the location will require one to take the mean of two numbers to calculate the median.
The result may or may not be an observed value as the example below illustrates. One shortcoming of the mean is that means are easily affected by extreme values. Measures that are not that affected by extreme values are called resistant.
Measures that are affected by extreme values are called sensitive. Using the data from Example , how would the mean and median change, if the entry 91 is mistakenly recorded as 9? The medians of the two sets are not that different. Therefore the median is not that affected by the extreme value 9. The mean is a sensitive measure or sensitive statistic and the median is a resistant measure or resistant statistic. After reading this lesson you should know that there are quite a few options when one wants to describe central tendency.
In future lessons, we talk about mainly about the mean. However, we need to be aware of one of its shortcomings, which is that it is easily affected by extreme values. Unless data points are known mistakes, one should not remove them from the data set! One should keep the extreme points and use more resistant measures. For example, use the sample median to estimate the population median. We say that the median is a resistant measure, whereas the mean is not a resistant measure.
A course has 2 sections, Section A and Section B. On the last exam, Section A's 10 students had A course has two sections, Section A and Section B. On the most recent exam, Section A's Jane has scores of 84, 92, and 89 on her first 3 exams. What does she need to score on the next Author information Copyright and License information Disclaimer. Assistant Editor, Journal of Pharmacology and Pharmacotherapeutics. E-mail: moc. This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.
This article has been cited by other articles in PMC. MEAN Mean is the most commonly used measure of central tendency. Table 1 Standard statistical notations.
Open in a separate window. Weighted mean Weighted mean is calculated when certain values in a data set are more important than the others. Geometric Mean It is defined as the arithmetic mean of the values taken on a log scale. Harmonic mean It is the reciprocal of the arithmetic mean of the observations. Manikandan S. Frequency distribution. J Phamacol Pharmacother. Statistics for the behavioral sciences. Belmont: Wadsworth — Thomson Learning; Introduction to biostatistics and research methods.
Medical statistics principles and methods.
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