# normality test spss

How to Shapiro Wilk Normality Test Using SPSS Interpretation | The basic principle that we must understand is that the normality test is useful to find out whether a research data is normally distributed or not normal. However, it is almost routinely overlooked that such tests are robust against a violation of this assumption if sample sizes are reasonable, say N ≥ 25. If the data are not normal, use non-parametric tests. One of the assumptions for most parametric tests to be reliable is that the data is approximately normally distributed. If you perform a normality test, do not ignore the results. SPSS Statistics Output. The hypotheses used in testing data normality are: Ho: The distribution of the data is normal Ha: The distribution of the data is not normal. 3. The normal distribution peaks in the middle and is symmetrical about the mean. Here two tests for normality are run. 4. Hence, a test can be developed to determine if the value of b 2 is significantly different from 3. If the data are normal, use parametric tests. If it is, the data are obviously non- normal. Just make sure that the box for “Normal” is checked under distribution. The Kolmogorov-Smirnov test is often to test the normality assumption required by many statistical tests such as ANOVA, the t-test and many others. Data does not need to be perfectly normally distributed for the tests to be reliable. You can reach this test by selecting Analyze > Nonparametric Tests > Legacy Dialogs > and clicking 1-sample KS test. In parametric statistical analysis the requirements that must be met are data that are normally distributed. You will now see that the output has been split into separate sections based on the combination of groups of the two independent variables. The Kolmogorov-Smirnov and Shapiro-Wilk tests can be used to test the hypothesis that the distribution is normal. Checking normality for parametric tests in SPSS . (SPSS recommends these tests only when your sample size is less than 50.) The test statistics are shown in the third table. This video demonstrates conducting the Shapiro-Wilk normality test in SPSS and interpreting the results. Recall that for the normal distribution, the theoretical value of b 2 is 3. The formal normality tests including Shapiro-Wilk test and Kolmogorov-Smirnov test may be used from small to medium sized samples (e.g., n < 300), but may be unreliable for large samples. This test checks the variable’s distribution against a perfect model of normality and tells you if the two distributions are different. Normal distributions can be divided up into the same proportions by the standard deviations, so 95% of the area under the curve lies within roughly plus or minus two standard deviations of the mean; In this video Jarlath Quinn demonstrates how to use the functions within the explore command in SPSS Statistics to test for normality. 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