Author: Wouter Zeevat

# Automated Statistical Test

#### Wouter Zeevat

# Introduction

The `automatedtests` package automatically selects and runs the most appropriate statistical test for your data, no manual decision-making needed. The function works with both individual vectors or a data frame and provides the results in an easy-to-understand format, which includes the test used and all the relevant statistics.

### Supported Tests

Number | Test
--- | ---
1 | One-proportion test
2 | Chi-square goodness-of-fit test
3 | One-sample Student’s t-test
4 | One-sample Wilcoxon test
5 | Multiple linear regression
6 | Binary logistic regression
7 | Multinomial logistic regression
8 | Pearson correlation
9 | Spearman’s rank correlation
10 | Cochran’s Q test
11 | McNemar’s test
12 | Fisher’s exact test
13 | Chi-square test of independence
14 | Student’s t-test for independent samples
15 | Welch’s t-test for independent samples
16 | Mann-Whitney U test
17 | Student’s t-test for paired samples
18 | Wilcoxon signed-rank test
19 | One-way ANOVA
20 | Welch’s ANOVA
21 | Repeated measures ANOVA
22 | Kruskal-Wallis test
23 | Friedman test

# Usage of `automatical_test()`

The `automatical_test()` function can be used with both individual vectors or a data frame. It automatically selects the most suitable statistical test based on the data provided.

## Example 1: Using Individual Vectors

In this example, we will use two vectors: `Species` and `Sepal.Length` from the `iris` dataset. We will use the `automatical_test()` function to automatically choose the best statistical test for these vectors.

    # Load the package
    library(automatedtests)

    # Example 1: Using individual vectors from the iris dataset
    test1 <- automatical_test(iris$Species, iris$Sepal.Length, identifiers = FALSE)

    ## Warning in automatical_test(iris$Species, iris$Sepal.Length, identifiers = FALSE): Normality test suggests the data may not be normally distributed.
    ##     It is recommended to visually inspect the data using a Q-Q plot.
    ##     If the data is in fact parametric but contains outliers,
    ##     consider manually applying normalization or transformation before proceeding

    # View the result summary
    print(test1$get_result())

    ##
    ##  Kruskal-Wallis rank sum test
    ##
    ## data:  data[[quan_index]] by data[[qual_index]]
    ## Kruskal-Wallis chi-squared = 96.937, df = 2, p-value < 2.2e-16

In this case, the function automatically selects the best statistical test based on the data’s distribution and other characteristics.

## Example 2: Forcing a Paired Test

Here, we simulate a before-and-after scenario, where data is collected before and after an intervention. The `automatical_test()` function can be instructed to use paired tests by setting the `paired` argument to `TRUE`.

    # Example 2: Forcing a paired test
    before <- c(200, 220, 215, 205, 210)
    after <- c(202, 225, 220, 210, 215)
    paired_data <- data.frame(before, after)

    # Perform the paired test
    test2 <- automatical_test(before, after, paired = TRUE)

    # View the result summary
    print(test2$get_result())

    ##
    ##  Paired t-test
    ##
    ## data:  data[[1]] and data[[2]]
    ## t = -7.3333, df = 4, p-value = 0.001841
    ## alternative hypothesis: true mean difference is not equal to 0
    ## 95 percent confidence interval:
    ##  -6.065867 -2.734133
    ## sample estimates:
    ## mean difference
    ##            -4.4

By setting `paired = TRUE`, the function forces the use of a paired statistical test, even if identifiers are not provided.

## Example 3: One-Sample Test with Custom Compare Value

You can override the default `compare_to` value to perform one-sample tests. For example, you can test whether the data differs significantly from a specified value.

    # Example 3: One-sample test
    test3 <- automatical_test(iris$Sepal.Length, compare_to = 5)

    ## Warning in automatical_test(iris$Sepal.Length, compare_to = 5): Normality test suggests the data may not be normally distributed.
    ##     It is recommended to visually inspect the data using a Q-Q plot.
    ##     If the data is in fact parametric but contains outliers,
    ##     consider manually applying normalization or transformation before proceeding

    # View the result summary
    print(test3$get_result()$p.value)

    ## [1] 1.297119e-19

In this case, `compare_to = 5` specifies that we are performing a one-sample test where we compare the `Sepal.Length` to the value 5.

# Conclusion

The `automatical_test()` function simplifies the process of selecting and running statistical tests. It automatically picks the most appropriate test based on the data’s structure and characteristics. You can fine-tune its behavior with options like `compare_to`, `identifiers`, and `paired`.

For more detailed information on the results of each test, you can use the `get_result()` method to retrieve a summary of the test performed.

# See Also

- `AutomatedTest` class for the object returned by the `automatical_test()` function.
- `automatedtests` package documentation.