Confidence intervals in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the mean of the sample data.

R Programming

mean_value <- [1](sample_data)

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

Amean

Bmedian

Csum

Dsd

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'median' instead of 'mean' will give the middle value, not the average.

Using 'sum' will add all values but not calculate the average.

The mean() function calculates the average value of the sample data, which is needed to compute the confidence interval.

2fill in blank

medium

Complete the code to calculate the standard error of the mean.

R Programming

std_error <- sd(sample_data) / sqrt([1](sample_data))

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

Alength

Bmean

Csum

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'sum' will add all values, which is not the sample size.

Using 'mean' or 'var' will not give the count of data points.

The standard error is the standard deviation divided by the square root of the sample size. The length() function returns the number of observations.

3fill in blank

hard

Fix the error in the code to calculate the confidence interval using the t-distribution.

R Programming

error_margin <- qt(1 - [1] / 2, df = length(sample_data) - 1) * std_error

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

A0.1

B0.05

C0.5

D0.01

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0.5 or 0.1 will give wrong quantiles and incorrect intervals.

Using 0.01 corresponds to 99% confidence, not 95%.

The confidence level is usually 95%, so the significance level alpha is 0.05. The code uses 1 - alpha/2 to get the correct quantile.

4fill in blank

hard

Fill both blanks to create the lower and upper bounds of the confidence interval.

R Programming

conf_interval <- c(mean_value [1] error_margin, mean_value [2] error_margin)

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

A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' for both bounds will give incorrect intervals.

Using '*' or '/' will cause wrong calculations.

The confidence interval lower bound is the mean minus the error margin, and the upper bound is the mean plus the error margin.

5fill in blank

hard

Fill all three blanks to calculate and print a 95% confidence interval for the sample mean.

R Programming

mean_value <- [1](sample_data)
std_error <- sd(sample_data) / sqrt([2](sample_data))
error_margin <- qt(1 - 0.05 / 2, df = [3](sample_data) - 1) * std_error

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

Amean

Blength

Dmedian

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'median' instead of 'mean' for the first blank.

Using 'sum' or other functions instead of 'length' for sample size.

The mean is calculated with mean(). The sample size is found with length(), used for standard error and degrees of freedom in qt().