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### 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 b**ias* 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 *d**escriptive statistics**.* These are numbers that describe a data set in terms of its important features: [more…]

### Displaying Your Statistical Data with Charts and Graphs

You can summarize your statistical data in a visual way using charts and graphs. These are displays that are organized to give you a big picture of the data in a flash and to zoom in on a particular result [more…]

### Why Margin of Error and Confidence Intervals Matter in Statistics

Statistical results should always include a margin of error and confidence intervals. This information is important because you often see statistics that try to estimate numbers pertaining to an entire [more…]

### How Hypothesis Tests Are Used in Statistics

One main staple of research studies is called hypothesis testing. A *hypothesis test* is a technique for using data to validate or invalidate a claim about a population. For example, a politician may claim [more…]

### Avoid Drawing the Wrong Conclusions from Statistical Data

Statistical formulas don’t know whether they are being used properly, and they don’t warn you when your results are incorrect. In order to draw the appropriate conclusions, it’s up to you to avoid overstating [more…]

### How to Spot Mathematical Errors in Statistical Data

After examining the design of the study and how data was collected, the next thing to do when you come upon a statistic or the result of a statistical study is to look for mathematical errors in the data [more…]

### Types of Statistical Data: Numerical, Categorical, and Ordinal

When working with statistics, it’s important to recognize the different types of data: numerical (discrete and continuous), categorical, and ordinal. *Data* [more…]

### What a *p*-Value Tells You about Statistical Data

When you perform a hypothesis test in statistics, a *p*-value helps you determine the significance of your results. Hypothesis tests are used to test the validity of a claim that is made about a population [more…]

### How Statistical Correlation and Causation Are Different

Of all of the misunderstood statistical issues, the one that’s perhaps the most problematic is the misuse of the concepts of correlation and causation. [more…]

### How to Break Down Categorical Statistics Using Two-Way Tables

You can break categorical data down using two-way tables (also known as contingency tables, cross-tabulations or crosstabs) to summarize statistical information about different groups. [more…]

### How to Calculate the Mean of a Statistical Data Set

The most common way to summarize a statistical data set is to describe where the center, or mean, is. One way of thinking about what the center of a data set means is to ask, “What’s a typical value?” [more…]

### How to Find the Median Value in a Statistical Data Set

The median is a statistic that is commonly used to measure the center of a data set. However, it is still an unsung hero of statistics in the sense that it isn’t used nearly as often as it should be, although [more…]