![]() ![]() For example, if you wanted to be 98 percent confident that your data was going to be reflective of the entire population then: If you’re a researcher you might want to figure out your own error tolerance Just subtract your confidence level from 1. The error tolerance, e, can be given to you (for example, in a question). If you have no idea about a population’s behavior, use Slovin’s formula to find the sample size.The formula (sometimes written as Sloven’s formula) was formulated by Slovin in 1960. But what if you knew nothing about your population? That’s where Slovin’s formula comes in. While there are many formulas to calculate sample sizes, most of them require you to know something about the population, like the mean. But would 100 people be sufficient? 1000? Ten thousand? How you figure out a big enough sample size involves applying a formula. Obviously, if you asked just one person in the population if they were vegetarian then their answer wouldn’t be representative of everyone. The problem with taking a sample of the population is sample size. The problems with surveying entire populations are why researchers survey just a fraction of the population: a sample. Think about how long it would take you to call over 300 million people Assuming they all had phones and could speak!. For example, let’s say you wanted to know how many people in the USA were vegetarians. It’s usually impossible to survey every member of a population because of money or time. Statistics is a way of looking at a population’s behavior by taking a sample. ![]() Slovins’s formula is used to calculate an appropriate sample size from a population. Like the explanation? Check out the Practically Cheating Statistics Handbook, which has hundreds more step-by-step explanations, just like this one! What is Slovin’s Formula? Step 3: Round your answer to a whole number (because you can’t sample a fraction of a person or thing!) In this example, we’ll use a 95 percent confidence level with a population size of 1,000. For example, you might want a confidence level of 95 percent (giving you an alpha level of 0.05), or you might need better accuracy at the 98 percent confidence level (alpha level of 0.02). ![]() Step 1: Figure out what you want your confidence level to be. Need help with a specific homework question? Check out our tutoring page.Įxample question: Use Slovin’s formula to find out what sample of a population of 1,000 people you need to take for a survey on their soda preferences. ![]()
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