The middle score for a set of data that has been arranged in order of magnitude

Measures of Central Tendancy

Measures of Central Tendencyare ways of describing the central position of a frequency distribution for a group of data.  You can describe this central position using the mean, median, or mode.  Which you use will depend on how much and the type of data you collected.

Type of Data for Responding Variable

Best Measure of Central Tendency

Qualitative
Nominal (no ranking or order)

Mode

Qualitative
Ordinal (has ranking or order)

Median

Quantitative 
With majority of skew values less than |1.0|

Mean

Quantitative
With majority of skew values more than |1.0|

Median

The arithmetic mean is the most commonly used measure of central tendency.  The mean is essentially a model of a data set for normally distributed (non-skewed) data.   The mean has one main disadvantage: it is particularly susceptible to the influence of outliers. These are values that are unusual compared to the rest of the data set by being especially small or large in numerical value. That’s why we determined the skew.

  • DO NOT calculate a mean for skewed data. 
  • DO NOT calculate a mean from values that are already averages. 
  • DO NOT calculate a mean when the measurement scale is not linear (i.e. pH units are not measured on a linear scale)


The mean is equal to the sum of all the values in the data set divided by the number of values in the data set. So, if we have N values in a data set and they have values x1,x2, … ,xn, the sample mean, usually denoted by (pronounced "x bar"), is:

The middle score for a set of data that has been arranged in order of magnitude

Calculating the Mean in Sheets

  • ​​In our class, the formula we'll want to  use is  =AVERAGE(A1:A100).  Replace A1:A100 with your data by highlighting the cells with data you want to include in the mean calculation.
  • Calculating the Mean in Google Sheets (website)
  • Finding the Mean in Google Sheets (video)
  • Changing the number of digits displayed in your Google Sheet (website)

Calculating the Mean in Excel

Open Excel and enter your data in columns.  You can label the columns if you prefer.  To calculate mean:

  • Click on the box in which you want the mean to be placed  
  • Click the "Formulas" tab at the top of the screen
  • Select the “Insert Function button”
  • A new box pops up.  Search to find the AVERAGE option, click OK  
  • Highlight the data of which you want the average to be calculated, click OK
  • Be sure your mean has the correct number of digits. Your processed data should have the same number of digits as your raw data.  To do this, click the box which is displaying the mean and on the "Home" tab click the decrease decimal button until you have the correct number of digits showing.

Median

Mode

Median

The median is the middle score for a set of data that has been arranged in order of magnitude. The median is less affected by outliers and skewed data. In order to calculate the median, suppose we have the data below:

65 55 89 56 35 14 56 55 87 45 92

We first need to rearrange that data into order of magnitude (smallest first):

14 35 45 55 55 56 56 65 87 89 92

Our median mark is the middle mark - in this case, 56 (highlighted in bold). It is the middle mark because there are 5 scores before it and 5 scores after it. This works fine when you have an odd number of scores, but what happens when you have an even number of scores? What if you had only 10 scores? Well, you simply have to take the middle two scores and average the result. So, if we look at the example below:

65 55 89 56 35 14 56 55 87 45

We again rearrange that data into order of magnitude (smallest first):

14 35 45 55 55 56 56 65 87

89

Only now we have to take the 5th and 6th score in our data set and average them to get a median of 55.5.

Mode:

The mode is the most frequent score in our data set. On a histogram it represents the highest bar in a bar chart or histogram. You can, therefore, sometimes consider the mode as being the most popular option. An example of a mode is presented below:

The middle score for a set of data that has been arranged in order of magnitude

Normally, the mode is used for categorical data where we wish to know which is the most common category, as illustrated below:

The middle score for a set of data that has been arranged in order of magnitude

We can see above that the most common form of transport, in this particular data set, is the bus. However, one of the problems with the mode is that it is not unique, so it leaves us with problems when we have two or more values that share the highest frequency, such as below:

The middle score for a set of data that has been arranged in order of magnitude

Is the middle score for a set of data arranged in order of magnitude?

The median of a data set is the middle value when the values are written in numerical order. If a data set has an even number of values, the median is the mean of the two middle values.

What is the middle score for a set of data?

The median is the middle score in the set. To find the median, start by arranging all of the data points from smallest to largest. In an odd-numbered set, the median will be the number in the very middle of the list. In an even-numbered set, you will need to calculate the average of the two middle numbers.

What is the middle score for a set of data that has been arranged from highest to lowest or lowest to highest?

The Median of a Data Set The median of a set of numbers is the middle number in the set (after the numbers have been arranged from least to greatest) -- or, if there are an even number of data, the median is the average of the middle two numbers.

What is the Middlemost score?

The median is the middlemost number. In other words, it's the number that divides the distribution exactly in half such that half the cases are above the median, and half are below. It's also known as the 50th percentile, and it can be calculated for ordinal and interval/ratio variables.