Summary statistics in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the mean of the numeric vector data.

R Programming

mean_value <- mean([1])

Drag options to blanks, or click blank then click option'

Asum

Bmean

Cdata

Dmedian

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the function name inside itself instead of the data vector.

Using sum or median instead of the data vector.

The mean() function calculates the average of the values in the vector data.

2fill in blank

medium

Complete the code to calculate the median of the numeric vector values.

R Programming

median_value <- median([1])

Drag options to blanks, or click blank then click option'

Amedian

Bvalues

Cmean

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using the function name median inside itself instead of the data vector.

Using mean or length instead of the data vector.

The median() function finds the middle value of the vector values.

3fill in blank

hard

Fix the error in the code to calculate the standard deviation of scores.

R Programming

std_dev <- sd([1])

Drag options to blanks, or click blank then click option'

Avar

Bsd

Cmean

Dscores

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the function name sd instead of the data vector.

Using mean or var instead of the data vector.

The sd() function calculates the standard deviation of the vector scores. You must pass the data vector, not the function name.

4fill in blank

hard

Fill both blanks to create a named list with mean and median of numbers.

R Programming

summary_stats <- list(mean = [1], median = [2])

Drag options to blanks, or click blank then click option'

Amean(numbers)

Bmedian(numbers)

Cmean

Dnumbers

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the function names mean or median without calling them.

Using the vector numbers directly instead of calculating the statistics.

Use mean(numbers) and median(numbers) to calculate the values and assign them to the list.

5fill in blank

hard

Fill all three blanks to create a data frame with mean, median, and standard deviation of data_vec.

R Programming

stats_df <- data.frame(
  Mean = [1],
  Median = [2],
  SD = [3]
)

Drag options to blanks, or click blank then click option'

Amean(data_vec)

Bmedian(data_vec)

Csd(data_vec)

Ddata_vec

Attempts:

3 left

💡 Hint

Common Mistakes

Using the vector data_vec directly instead of calculating statistics.

Mixing up the order of mean, median, and standard deviation.

Calculate mean, median, and standard deviation of data_vec and assign them to the data frame columns.

Practice

1. What does the summary() function in R provide when applied to a numeric vector?

easy

A. Minimum, 1st quartile, median, mean, 3rd quartile, and maximum values

B. Only the mean and median values

C. The sum and product of all elements

D. The count of unique values

Solution

1. Step 1: Understand what summary() does for numeric vectors

   The summary() function returns key statistics including minimum, quartiles, median, mean, and maximum.

2. Step 2: Compare options with the known output

   Minimum, 1st quartile, median, mean, 3rd quartile, and maximum values lists all these statistics correctly, while others miss important parts or give unrelated info.

3. Final Answer:

   Minimum, 1st quartile, median, mean, 3rd quartile, and maximum values -> Option A

4. Quick Check:

   summary() = min, Q1, median, mean, Q3, max [OK]

Hint: Remember summary() shows min, quartiles, median, mean, max [OK]

Common Mistakes:

• Thinking summary() only gives mean and median
• Confusing summary() with sum() or length()
• Expecting summary() to count unique values

2. Which of the following is the correct way to get summary statistics of a data frame named df in R?

easy

A. stats(df)

B. summarize(df)

C. summary(df)

D. summary_stats(df)

Solution

1. Step 1: Recall the correct function name for summary statistics in R

   The built-in function to get summary statistics is summary().

2. Step 2: Check the options for correct syntax

   Only summary(df) uses the correct function summary() applied to the data frame df.

3. Final Answer:

   summary(df) -> Option C

4. Quick Check:

   summary() is the correct function [OK]

Hint: Use summary() for data frames, not summarize() or others [OK]

Common Mistakes:

• Using summarize() which is from dplyr, not base R
• Typing summary_stats() which doesn't exist
• Using stats() which is unrelated

3. What will be the output of the following R code?

vec <- c(5, 10, 15, 20, 25)
summary(vec)

medium

A. Min. 5, 1st Qu. 10, Median 15, Mean 15, 3rd Qu. 20, Max. 25

B. Min. 5, Median 10, Mean 15, Max. 25

C. Min. 5, Max. 25, Sum 75

D. Error: summary() cannot be applied to vectors

Solution

1. Step 1: Calculate summary statistics for the vector

   The vector is 5, 10, 15, 20, 25. Minimum is 5, 1st quartile is 10, median is 15, mean is (5+10+15+20+25)/5 = 15, 3rd quartile is 20, maximum is 25.

2. Step 2: Match calculated values with options

   Min. 5, 1st Qu. 10, Median 15, Mean 15, 3rd Qu. 20, Max. 25 matches all these values exactly. Other options miss quartiles or give errors.

3. Final Answer:

   Min. 5, 1st Qu. 10, Median 15, Mean 15, 3rd Qu. 20, Max. 25 -> Option A

4. Quick Check:

   summary(vec) = min 5, Q1 10, median 15, mean 15, Q3 20, max 25 [OK]

Hint: Calculate min, quartiles, median, mean, max for vector [OK]

Common Mistakes:

• Forgetting to calculate quartiles
• Confusing median with mean
• Expecting an error for summary() on vectors

4. Identify the error in this R code that tries to get summary statistics of a numeric vector nums:

summary(nums, digits=2)

medium

A. The vector nums must be sorted before summary()

B. The vector nums must be converted to a data frame first

C. The function should be summarize() instead of summary()

D. The summary() function does not have a digits argument

Solution

1. Step 1: Check the arguments of summary() in R

   The base R summary() function does not accept a digits argument. This causes an error.

2. Step 2: Verify other options

   Converting to data frame or sorting is not required. summarize() is from dplyr, not base R.

3. Final Answer:

   The summary() function does not have a digits argument -> Option D

4. Quick Check:

   summary() has no digits argument [OK]

Hint: Check function arguments carefully to avoid errors [OK]

Common Mistakes:

• Assuming summary() accepts digits argument
• Thinking vector must be data frame
• Confusing summary() with dplyr's summarize()

5. You have a data frame df with a numeric column age. You want to find the median age but exclude any missing values (NA). Which R code correctly does this?

hard

A. median(df$age)

B. median(df$age, na.rm = TRUE)

C. summary(df$age, na.rm = TRUE)["Median"]

D. summary(df$age)$median

Solution

1. Step 1: Understand how to calculate median excluding NA values

   The median() function has an argument na.rm = TRUE to remove missing values before calculation.

2. Step 2: Check each option for correctness

   median(df$age, na.rm = TRUE) correctly uses median() with na.rm = TRUE. summary(df$age, na.rm = TRUE)["Median"] tries to extract median from summary but summary() does not accept na.rm. median(df$age) ignores NA values causing NA result. summary(df$age)$median tries to access median as a list element which is invalid.

3. Final Answer:

   median(df$age, na.rm = TRUE) -> Option B

4. Quick Check:

   Use median() with na.rm=TRUE to exclude NA [OK]

Hint: Use median(..., na.rm=TRUE) to ignore missing values [OK]

Common Mistakes:

• Not using na.rm=TRUE causing NA result
• Trying to get median from summary() output incorrectly
• Assuming summary() removes NA automatically