Topic

Descriptive statistics and data screening

Descriptive statistics, normality tests, outliers and missing data: how to screen and describe your data before analysis.

How to Test for Normality (and What to Do If Your Data Aren’t Normal)

A practical guide to checking normality with plots and tests, understanding what really needs to be normal, and choosing the right fix when your data are skewed.

October 13, 20264 min read

Free Descriptive statistics and data screening tools

All 90+ tools →

Bar Graph with Error BarsFree bar graph with error bars: plot group means with standard deviation, standard error or 95% confidence interval error bars, including clustered bars.Box Plot Maker (Box and Whisker Plot)Free box plot maker: box-and-whisker plots for several variables or groups, with the five-number summary, IQR, mean and a list of outliers.Confidence Interval CalculatorCalculate a 90%, 95% or 99% confidence interval and margin of error for a mean (t distribution) or a proportion (Wilson score). Free and instant.Descriptive Statistics CalculatorFree descriptive statistics calculator: mean, median, mode, SD, quartiles, skewness, frequency tables, pie charts, histograms and box plots for many variables.Histogram MakerFree histogram maker: draw a histogram with an optional normal curve, choose the number of bins, and get a grouped frequency distribution table.P-Value CalculatorFind the exact p-value from a t, z, F, chi-square or correlation statistic and its degrees of freedom. One- or two-tailed, free and instant.Pie Chart Maker and Frequency TableFree online pie chart maker: create pie, doughnut and bar charts with percentages and a frequency table from raw survey data or a table of counts.Scatter Plot MakerFree scatter plot maker: plot two variables, colour points by group, and add a trend line with its regression equation, R² and Pearson correlation.Shapiro-Wilk Normality Test CalculatorTest normality online with the Shapiro-Wilk and Kolmogorov-Smirnov (Lilliefors) tests, skewness and kurtosis z-scores, a Q-Q plot and histogram. Free.Z-Score CalculatorConvert a raw score to a z-score and find the percentile and probability below, above or between values on the normal curve. Free with a shaded graph.