This Scribe shows you how to use the [[countif]] function in Google Sheets to count instances in a dataset based on 1 single criteria. For multiple criteria, use the [[countifs]] function

Select the cell where you want your output to live

Let's assume you want to count how many people named "Joe" are in this dataset. 
In the cell, type "=countif(A2:A7,"Joe")" and hit [[enter]]

The [[countif]] syntax is as follows:
=COUNTIF(RANGE,CRITERIA)

Google Sheets is a powerful online tool to help you do quantitative analysis. Learn how to use formulas to manipulate and analyze datasets, such as Google Sheets' COUNTIF and SUMIF functions, among many others.

How to use "countif" in Google Sheets