Final answer:
To find the middle 50% of the ages for the Crest brand, calculate the first quartile (Q1), the third quartile (Q3), and subtract Q1 from Q3 to find the interquartile range (IQR).
Step-by-step explanation:
To calculate the middle 50% of the ages for the Crest brand, we need to find the first quartile (Q1) and the third quartile (Q3). Q1 is the median of the lower half of the data and Q3 is the median of the upper half of the data. To find the interquartile range (IQR), subtract Q1 from Q3. With the provided data, the middle 50% of the ages for the Crest brand is 24.5 years.
Learn more about Interquartile Range