57 61 50 54 54 54 56 54 61 54 48 49 42 51 61 57 68 65 50 51 60 52 57 51 52 47 56 62 69 58 49 56 55 55 43 64 57 64 46 55 51 55 46 before you can make a frequency table, you need to decide how to set up the age intervals. what is the best way to group these ages into six intervals?

I would look through the numbers to determine their range. It appears to me to be 42 to 69. This suggests a frequency table with numbers 40 to 70, a range easily divided into 6 parts.

Since the width of each group will be (70 -40)/6 = 5, you have to decide on the group boundaries. It might work well to subtract 1/2 from the numbers 40, 45, 50, 55, 60, 65 to define the boundary. That way, for the integers given, you have
.. group 1 = 40 ≤ age < 45
.. group 2 = 45 ≤ age < 50
.. group 3 = 50 ≤ age < 55
.. group 4 = 55 ≤ age < 60
.. group 5 = 60 ≤ age < 65
.. group 6 = 65 ≤ age < 70