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The table gives information about the speeds, in kilometres per hour, of 80 motorbikes as each pass under a bridge.
Speed
(s kilometres per hour) Frequency
40 < s  50 10
50 < s  60 16
60 < s  70 19
70 < s  80 23
80 < s  90 12
(a) Write down the modal class
(b) Work out an estimate for the mean speed of the motorbikes as they pass under the bridge.
Give your answer correct to 3 significant figures.

Respuesta :

MrRoyal

The modal class is 70 - 80 and the mean speed is 66.4

How to determine the modal class?

The table of values is given as:

Speed    Frequency

40 - 50          10

50 - 60          16

60 - 70          19

70 - 80          23

80 - 90          12

The modal class is the class with the highest frequency

The class 70 - 80 has the highest frequency of 23

Hence, the modal class is 70 - 80

How to determine the mean?

Rewrite the frequency table to include the class midpoints

x             f

45          10

55          16

65          19

75          23

85          12

The estimate of the mean speed is then calculated as:

[tex]\bar x =\frac{\sum fx}{\sum f}[/tex]

So, we have:

[tex]\bar x = \frac{45* 10 + 55 * 16 + 65 * 19 + 75 * 23 + 85 * 12}{80}[/tex]

Evaluate

[tex]\bar x = 66.4[/tex]

Hence, the mean speed is 66.4

Read more about mean and mode at:

https://brainly.com/question/14532771

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