Question

Refer to the accompanying data set and use the 25 home voltage measurements to construct a frequency distribution with five classes. Begin with a lower class limit of

127.7127.7

​volts, and use a class width of 0.2 volt. Does the result appear to have a normal​ distribution? Why or why​ not?

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Complete the frequency distribution below.

Voltage​ (volts)	Frequency
127.7127.7minus−nothing	nothing
nothingminus−nothing	nothing
nothingminus−nothing	nothing
nothingminus−nothing	nothing
nothingminus−nothing	nothing

​(Type integers or decimals rounded to the nearest tenth as​ needed.)

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Voltage Measurements From a Home

nbsp Day nbsp Day	nbsp Home nbsp Home ​(volts)	nbsp Day nbsp Day	nbsp Home nbsp Home ​(volts)	nbsp Day nbsp Day	nbsp Home nbsp Home ​(volts)	nbsp Day nbsp Day	nbsp Home nbsp Home ​(volts)	Full data set
1	128.0128.0	8	128.0128.0	15	128.4128.4	22	128.2128.2
2	128.3128.3	9	128.2128.2	16	128.2128.2	23	127.9127.9
3	128.2128.2	10	128.4128.4	17	127.8127.8	24	128.0128.0
4	128.3128.3	11	128.2128.2	18	127.9127.9	25	128.1128.1
5	128.4128.4	12	128.1128.1	19	128.1128.1
6	127.8127.8	13	128.1128.1	20	128.6128.6
7	128.2128.2	14	128.2128.2	21	128.4128.4

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Answer 1

a) frequency distribution with five classes beginning with a lower class limit of 127.7 volts, and use a class width of 0.2 volt

voltage(volts) freq

[127.7-127.9) 2
[127.9-128.1) 5
[128.1-128.3) 11
[128.3-128.5) 6
[128.5-128.7) 1

we have made frequency distribution with 0.2 class width as you can see that the next voltage below 127.9 is 128.1 with the difference of 0.2 volts and so on till we have achieved our five classes.

we noted the frequency of each voltage by counting how many times it has appeared in these specified class intervals as in this question 127.8 appeared two times and belongs to the class interval (127.7 to 127.9). Thus it's frequesny is 2. Similarly we have done it for all the five classes.

b)  Yes, the frequency distribution appears to be normal because the frequencies start low, reach a maximum, then become low again, and are roughly symmetric about the maximum frequency.