1. Introduction to statistics
Welcome to the course! I'm Ted and I'll be your instructor. What is a statistic? It's just a piece of information from a large quantity of data. Simply put, a statistic describes data in some way, and in this course, you'll learn about different statistics you can use to extract insights from your data.
2. Sometimes it's ok to be mean (average)!
Let's begin with averages. An average is an information reduction technique. You start with a data population which may be too large to understand so you need a way to reduce the amount of information into a comprehensible amount. For example, there are 126 million people living in Japan. That's a lot of people! You could look at a list of every person & their age to intuit something about the population's age. However, it's easier to take a mean average to understand the population.
3. What it takes to be mean (average)?
A mean is the sum of all observations in your population or sample divided by the number of observations in that population or sample.
4. Let's calculate an average
This is a sample of 10 Japanese ages. Summing the ages, you get 473. Therefore the mean average is 473 divided by 10 or 47.3. Mean reduces information from these 10 observations to one value. Let's compare Japan's average age, 47.3 to Uganda's average age.
5. Let's calculate another average
The Ugandan sample sums to 158 & the count is 10. Thus the Ugandan mean is 15.8. Comparing the two samples Ugandans have a lower average age compared to Japan. In this example you didn't have to compare all 20 samples to arrive at this conclusion, simply taking an average of each was enough to help you learn about the sample differences.
6. Median averages
Another average is the "median". The median is the middle number of a data set. When sorted from smallest to largest half the numbers are less than the median & half the numbers are above the median. The Japanese ages have been sorted,
7. Median averages
and to make it clear the Person column has the top & bottom 4 values crossed off. This leaves 47 & 48 in the middle. The median lies in between 47 & 48, which is 47.5. If our sample had an odd number of observations, such as 9, the middle number would have just been 47. An advantage of the median compared to the mean is that it is more robust to outliers, so if your dataset has any outliers, the median may be a more informative statistic.
8. Modal average
The final statistic we'll cover here is the mode. The mode is a number that appears most often in a dataset. This Japanese age sample has 48 listed twice. Thus, the mode average is 48.
9. Mean average in Google Sheets
You can use spreadsheet functions to easily and quickly calculate the mean, median, and mode. Let's go over these now.
10. Mean average in Google Sheets
you can calculate a mean using the AVERAGE function.
11. Mean average in Google Sheets
Here, we're passing in a range consisting of the cells B2 through B11 to the average function to calculate the mean.
12. Median and Mode in Google Sheets
To calculate the median, use "MEDIAN" - no surprise there - and use "MODE" to calculate a dataset's mode.
13. Let's practice some averages!
Let's practice calculating some spreadsheet averages!