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Using Linear Regression to Predict an Outcome

Statistical researchers often use a linear relationship to predict the (average) numerical value of Y for a given value of X using a straight line (called the [more…]

How to Calculate a Regression Line

In statistics, you can calculate a regression line for two variables if their scatterplot shows a linear pattern and the correlation between the variables is very strong [more…]

How to Interpret a Regression Line

In statistics, once you have calculated the slope and y-intercept to form the best-fitting regression line in a scatterplot, you can then interpret their values. [more…]

How to Calculate a Confidence Interval for a Population Mean When You Know Its Standard Deviation

If you know the standard deviation for a population, then you can calculate a confidence interval (CI) for the mean, or average, of that population. When a statistical characteristic that’s being measured [more…]

How to Compare Two Population Proportions

For statistical purposes, you can compare two populations or groups when the variable is categorical (for example, smoker/nonsmoker, Democrat/Republican, support/oppose an opinion, and so on) and you’re [more…]

Working with Statistical Two-Way Tables

To explore the links between two categorical variables, you first need to organize the data that’s been collected, and a table is a great way to do that. A [more…]

Why the Statistical Mean and Median of a Histogram Often Have Different Centers

A histogram gives you a rough idea of where the "center" of the data lies. The word center is in quotes because many different statistics are used to designate the center. The two most common measures [more…]

How to Find the Interquartile Range for a Statistical Sample

To obtain a measure of variation based on the five-number summary of a statistical sample, you can find what's called the interquartile range, or IQR.

The purpose of the five-number summary is to give descriptive [more…]

How a Pie Chart Reflects Categorical Data in a Statistical Data Set

A pie chart takes categorical data from a statistical sample and breaks them down by group, showing the percentage of individuals that fall into each group. Because a pie chart takes on the shape of a [more…]

How to Interpret a Statistical Bar Graph

A bar graph (or bar chart) is perhaps the most common statistical data display used by the media. A bar graph breaks categorical data down by group, and represents these amounts by using bars of different [more…]

How Graphs Can Distort Statistics

A statistical graph can give you a false picture of the statistics on which it is based. For example, it can be misleading through its choice of scale on the frequency/relative frequency axis [more…]

How Histograms Show Statistical Data

A histogram is a special graph applied to statistical data broken down into numerically ordered groups; for example, age groups such as 10–20, 21–30, 31–40, and so on. A histogram provides a snapshot of [more…]

How to Group Statistical Data Appropriately in a Histogram

When you create a histogram, it's important to group the data sets into ranges that let you see meaningful patterns in your statistical data. For example, say you want to see if actresses who have won [more…]

How to Place Borderline Statistical Values in a Histogram

When you create a histogram, you need to divide the data set into separate groups. However, some statistical data may be right on the borderline between two groups. What do you do in these situations? [more…]

How to Clearly Label the Axes on a Statistical Histogram

The most complex part of interpreting a statistical histogram is to get a handle on what you want to show on the x and y axes. Having good descriptive labels on the axes will help. Most statistical software [more…]

How Histograms Can Misrepresent Statistical Data

There are no hard and fast rules for how to create a histogram based on a set of statistical data; the person making the graph gets to choose the groupings on the [more…]

Why You Need to Identify a Population for Statistical Research

For virtually any statistical study of a population, you have to center your attention on a particular group of individuals (for example, a group of people, cities, animals, rock specimens, exam scores [more…]

Avoid Bias with Random Statistical Samples

How do you select a statistical sample in a way that avoids bias? The key word is random. A random sample is a sample selected by equal opportunity; that is, every possible sample of the same size as yours [more…]

How to Identify Statistical Bias

Bias is a word you hear all the time in statistics, and you probably know that it means something bad. But what really constitutes bias? Bias is systematic favoritism that is present in the data collection [more…]

Why Mean and Median Are Both Important in Statistical Data

In statistics, the average and the median are two different representations of the center of a data set and can often give two very different stories about the data, especially when the data set contains [more…]

What the Distribution Tells You about a Statistical Data Set

The distribution of a statistical data set (or a population) is a listing or function showing all the possible values (or intervals) of the data and how often they occur. When a distribution of categorical [more…]

Comparing Statistical Surveys and Statistical Experiments

There are two major types of statistical studies: surveys and experiments. After a question has been formed, researchers must design an effective study to collect data that will help answer that question [more…]

Identifying Bad Statistical Samples

After a statistical study has been designed, be it a survey or an experiment, you need to select a sample of individuals who represent a cross-section of the entire population. This is critical to producing [more…]

Identifying Statistical Bias in Your Data Sample

Statistical bias is the systematic favoritism of certain individuals or certain responses in a study. Bias is the nemesis of statisticians, and they do everything they can to avoid it. Want an example [more…]

Describing Your Statistical Data with Numbers

After collecting good statistical data, you can summarize it with descriptive statistics. These are numbers that describe a data set in terms of its important features: [more…]

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