# What is a statistical study?

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A statistical study is an investigation that uses quantitative methods to collect, analyze, and interpret data to make informed decisions or draw conclusions. It aims to understand trends, relationships, and patterns within a specific context, often using a larger population sample. To help you better understand this concept, think of a statistical study as a puzzle, where each piece represents a different component that, when put together, helps us see the bigger picture.

Now let’s explore each component of a statistical study through real-world examples:

1. Population: A population is the entire group of individuals or objects that we want to study. For example, a news report states, “the average height of adult males in the United States is 5 feet 9 inches.” In this case, the population is all adult males in the United States.
2. Sample: A sample is a smaller subset of the population chosen to represent the larger group. The news report might mention that “a random sample of 1,000 adult males was surveyed.” This sample of 1,000 adult males represents the larger population of adult males in the United States.
3. Population Size: This refers to the total number of individuals or objects in the population. In our example, the population size is the total number of adult males in the United States.
4. Sample Size: The sample size is the number of individuals or objects included in the sample. In our example, the sample size is 1,000 adult males.
5. Population Parameter: A population parameter is a numerical value that describes a specific characteristic of the entire population. It is the value we want to know about the population. In the news report, the population parameter is the average height of all adult males in the United States.
6. Sample Statistic: A sample statistic is a numerical value that describes a specific characteristic of the sample. This value helps us draw conclusions about the population parameter. The news report might state that “the average height of the 1,000 adult males surveyed was 5 feet 8.9 inches.” This is the sample statistic.
7. Margin of Error: The margin of error is the range within which we expect the true population parameter to fall, given our sample statistic. The news report might include a statement like “the margin of error for the average height is plus or minus 0.5 inches.”
8. Confidence Interval: A confidence interval is a range within which we expect the true population parameter to fall with a specified level of confidence. In the news report, the confidence interval for the average height could be expressed as “5 feet 8.4 inches to 5 feet 9.4 inches with a 95% confidence level.”
9. Confidence Level: The confidence level represents the likelihood that the true population parameter falls within the confidence interval. In our example, the 95% confidence level means that we can be 95% confident that the true average height of adult males in the United States lies between 5 feet 8.4 inches and 5 feet 9.4 inches.

By understanding these components, we can better interpret and evaluate the results of statistical studies, making more informed decisions based on the data presented.