# Descriptive statistics

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The tutorial is based on R and StatsNotebook, a graphical interface for R.

This tutorial will give a short introduction on descriptive analysis using **StatsNotebook**. Descriptive statistics such as mean, standard deviation, median and interquartile range can be easily obtained using the **Explore** panel.

We use the built-in **Personality** dataset in this example. This dataset can be loaded into **StatsNotebook** using the instructions provided here or can be downloaded from
here
.

The **Personality** dataset contains data from 231 participants, with measures on the Big 5 personality factors (*Agreeableness*, *Conscientiousness*, *Extraversion*, *Neuroticism* and *Openness*), and three measures of mental health (*Depression*, *Trait anxiety* and *State anxiety*). It also contains data on participants’ sex.

We will demonstrate how to generate simple descriptive statistics, and how to generate descriptive statistics by group.

#### Descriptive statistics

To calculate descriptive statistics,

- Click
**Analysis**at the top - Click
**Explore** - Select
**Descriptive statistics**on the menu - Select variables into
**Target Variables**on the right. In this example, we will select*Neuroticism*,*Depression*and*Sex*.**Sex**is a categorical variable. If it is not yet coded as a**factor**, we will need to manually convert it into a**factor**variable.

- Expand the
**Statistics and plots**panel, by default,**mean**and**standard deviation**are calculated for a numeric variable (*Neuroticism*and*Depression*);**count**is calculated for a categorical (factor) variable (*Sex*). Additional statistics, such as**median**and**interquartile range**can be requested here.

##### R codes – Descriptive statistics

The following is the R code generated by **StatsNotebook**. We will explain these codes in the next section.

library(tidyverse) library(e1071) library(ggplot2) library(GGally) "Sample size and missing data" currentDataset %>% summarize(count = n(), mis_Neuroticism = sum(is.na(Neuroticism)), mis_Depression = sum(is.na(Depression)), mis_Sex = sum(is.na(Sex)) ) "Descriptive Statistics for numeric variables" currentDataset %>% summarize(count = n(), M_Neuroticism = mean(Neuroticism, na.rm = TRUE), M_Depression = mean(Depression, na.rm = TRUE), SD_Neuroticism = sd(Neuroticism, na.rm = TRUE), SD_Depression = sd(Depression, na.rm = TRUE) ) %>% print(width = 1000, n = 500) ggplot(currentDataset) + geom_qq(aes(sample=Neuroticism)) ggplot(currentDataset) + geom_qq(aes(sample=Depression)) ggplot(currentDataset) + geom_histogram(aes(x=Neuroticism), color = "white") ggplot(currentDataset) + geom_histogram(aes(x=Depression), color = "white") "Counts for categorical variables" currentDataset %>% drop_na(Sex) %>% group_by(Sex) %>% summarize(count = n()) %>% spread(key = Sex, value = count) ggplot(currentDataset) + geom_bar(stat = "count", aes(x=Sex)) "Chan, G. and StatsNotebook Team (2020). StatsNotebook. (Version 0.1.0) [Computer Software]. Retrieved from https://www.statsnotebook.io" "R Core Team (2020). The R Project for Statistical Computing. [Computer software]. Retrieved from https://r-project.org"

##### R codes explained – Descriptive statistics

The following is from the top section of the generated codes.

library(tidyverse) library(e1071) library(ggplot2) library(GGally) "Sample size and missing data" currentDataset %>% summarize(count = n(), mis_Neuroticism = sum(is.na(Neuroticism)), mis_Depression = sum(is.na(Depression)), mis_Sex = sum(is.na(Sex)) )

First we load all the necessary libraries for this analysis, and then calculate the sample size and missing data in each of the variables. The above codes produce the summary below. Overall, there are 231 rows of data (**N = 231**). There are **14** missing data points for *Neuroticism* and **33** missing data points for *Depression*. There is no missing data for *Sex*.

###################################################### [1] "Sample size and missing data" ###################################################### # A tibble: 1 x 4 count mis_Neuroticism mis_Depression mis_Sex1 231 14 33 0 ######################################################

The following code is then used to calculate the descriptive statistics for the numeric variables (*Neuroticism* and *Depression*).

print("Descriptive Statistics") "Descriptive Statistics for numeric variables" currentDataset %>% summarize(count = n(), M_Neuroticism = mean(Neuroticism, na.rm = TRUE), M_Depression = mean(Depression, na.rm = TRUE), SD_Neuroticism = sd(Neuroticism, na.rm = TRUE), SD_Depression = sd(Depression, na.rm = TRUE) ) %>% print(width = 1000, n = 500)

This code produces the following output. The mean of *Neuroticism* and *Depression* are **87.7** (SD = 7.06) and **23.1** (SD = 5.81) respectively.

###################################################### [1] "Descriptive Statistics for numeric variables" ###################################################### # A tibble: 1 x 5 count M_Neuroticism M_Depression SD_Neuroticism SD_Depression1 231 87.7 7.06 23.1 5.81 ######################################################

The following code is then used to produce normality plots and histograms.

ggplot(currentDataset) + geom_qq(aes(sample=Neuroticism)) ggplot(currentDataset) + geom_qq(aes(sample=Depression)) ggplot(currentDataset) + geom_histogram(aes(x=Neuroticism), color = "white") ggplot(currentDataset) + geom_histogram(aes(x=Depression), color = "white")

The top two plots are for *Neuroticism* and the bottom two for *Depression*. The left plots are normality plots. If the data is normally distributed, the points will roughly follow a straight line. The histograms on the right show the distribution of the variables. These plots show that the distribution of *Neuroticism* is approximately normal, but *Depression* is skewed to the right.

Lastly, the following codes are used to calculate the frequency count for the categorical variable *Sex* and to generate a simple bar graph.

"Counts for categorical variables" currentDataset %>% drop_na(Sex) %>% group_by(Sex) %>% summarize(count = n()) %>% spread(key = Sex, value = count) ggplot(currentDataset) + geom_bar(stat = "count", aes(x=Sex))

Below is the output from **StatsNotebook**. Of the 231 participants, 70 are female and 161 are male.

# A tibble: 1 x 2 Female Male1 70 161

#### Descriptive statistics by group

In this example, we will generate the descriptive statistics of *Neuroticism* and *Depression* by *Sex*.

To do this, we can

- Click
**Analysis**at the top - Click
**Explore** - Select
**Descriptive statistics**on the menu - Select variables into
**Target Variables**on the right. In this example, we will select*Neuroticism*and*Depression*. - Select the grouping variable (
*Sex*) into**Split by**box on the right.**Sex**is a categorical variable. If it is not yet coded as**factor**, we will need to manually convert it into a**factor**variable.

- Expand the
**Statistics and plots**panel, by default,**mean**and**standard deviation**are calculated for numeric variables (*Neuroticism*and*Depression*). Additional statistics, such as**median**and**interquartile range**can be requested here.

##### R codes – Descriptive statistics by group

This code is very similar to those above, except now we have specified that the analysis split by group (*Sex*).

library(tidyverse) library(e1071) library(ggplot2) library(GGally) "Sample size and missing data" currentDataset %>% summarize(count = n(), mis_Neuroticism = sum(is.na(Neuroticism)), mis_Depression = sum(is.na(Depression)), mis_Sex = sum(is.na(Sex)) ) "Descriptive Statistics for numeric variables" currentDataset %>% group_by(Sex) %>% summarize(count = n(), M_Neuroticism = mean(Neuroticism, na.rm = TRUE), M_Depression = mean(Depression, na.rm = TRUE), SD_Neuroticism = sd(Neuroticism, na.rm = TRUE), SD_Depression = sd(Depression, na.rm = TRUE) ) %>% print(width = 1000, n = 500) ggplot(currentDataset) + geom_qq(aes(sample=Neuroticism)) + facet_wrap(~Sex) ggplot(currentDataset) + geom_qq(aes(sample=Depression)) + facet_wrap(~Sex) ggplot(currentDataset) + geom_histogram(aes(x=Neuroticism), color = "white") + facet_wrap(~Sex) ggplot(currentDataset) + geom_histogram(aes(x=Depression), color = "white") + facet_wrap(~Sex) "Chan, G. and StatsNotebook Team (2020). StatsNotebook. (Version 0.1.0) [Computer Software]. Retrieved from https://www.statsnotebook.io" "R Core Team (2020). The R Project for Statistical Computing. [Computer software]. Retrieved from https://r-project.org"

The output from **StatsNotebook** are very similar to what we have before but is now stratified by *Sex*.

###################################################### # A tibble: 2 x 6 Sex count M_Neuroticism M_Depression SD_Neuroticism SD_Depression1 Female 70 96.2 8.74 23.0 5.87 2 Male 161 83.8 6.16 22.2 5.60 ######################################################

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