To solve the exercise, we add the frequency between the intervals 5.5 - 6.5, 6.5 - 7.5, and 7.5 - 8.5:
• Frequency between 5.5 and 6.5: 7
,
• Frequency between 6.5 and 7.5: 5
,
• Frequency between 7.5 and 8.5: 5
Therefore, there are 17 values in the data set between 5.5 and 8.5.