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1. Compute for the mean, median, and mode of the lengths of mosquitoes' lives in seconds after being sprayed with Insecticide A.

13     14     23     22     16     25     14     25     17     28     22
33     33     22     22     16     13     24     25     35     14     17
15     34     36     25     18     27     38     17     18     28     28
28     38       7     17       7    16     26      5      15     15     18
29     27     36     38     17     18     24     23     35     34     16
14     26     14     26       5     25     34     16     27       6     37
14     26     37     36     17     26     40     26     35      13    25

2. Calculate the mean, median, and mode of the scores below:

Scores      f
95-99      17
90-94      20
85-89      25
80-84      18
75-79      12
70-74       8

### 1 Answer by Expert Tutors

Matthew B. | Statistics | SPSS | RStatistics | SPSS | R
4.9 4.9 (261 lesson ratings) (261)
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To find the mean use the following formula (∑x)/N or the sum of all x values divided by the number of cases. In this case, N = 77 and ∑x can be calculated in a pretty straightforward albeit time-consuming computations. You can also enter this data into Excel or another statistics program and ask the software to do the heavy lifting. The median should be able to be calculated similarly. Or you can sort the data and identify the value above which half the values fall. A similar approach can be used for determining the mode: sorting the data and count the number of instances for each value.

In the first data matrix the M = 22.6, median = 23, and there are four modal values each with 6 instances (14, 17, 25, 26).

I have to be honest in that the second set of data is somewhat less straightforward in terms of what it represents and how it should be interpreted in the context of these measures of central tendency. Without understanding more I don't want to offer any specific values or advice on how to approach such data.