5) TRUE or FALSE? At least 95% of all the scores are with in 2 standard deviatio

Question

5) TRUE or FALSE? At least 95% of all the scores are with in 2 standard deviations of the mean. Any time the test statistic is close to 1 , you may accept the claim as true. _ 11 IS possable to prove that the means of two populations are equal. The mean of all sample standard deviations is equal to the overall standard deviation The mean of all sample means is equal to the overall mean To score at the 98* centile means that the person got 98% of the questions ight. Using statistics it is possible to prove that smoking causes cancer Normal distributions are made from histograms. Two samples are independent if the chi-squared test statistic is below 1.0 6) Listed below are the ages of Hartnell College students 19.21,26, 25,20, 18, 17,45,23,26,21.20, 19.25, 24, 26,51,39. 17 a) Find the age at the 33" percentile. b) Find the mean and the median c) Create a frequency table with 3 classes d) Assuming there is a normal distribution for these ages, find the probabilty that a stadent is at least 21 years old.

Explanation / Answer

SOlution6a:

age at 33 percentile=20

Used R code:

Ages <- c(19,21,26,25,20,18,17,45,23,26,21,20,19,25,24,26,51,39,17
)
quantile(Ages, c(.33))

Solution6b:

mean=25.36842

median=23

rcode:

Ages <- c(19,21,26,25,20,18,17,45,23,26,21,20,19,25,24,26,51,39,17)

mean(Ages)
median(Ages)

Solution6c:

Class count

17-30 16

31-44 1

45-58 2

Solutiond:

standard deviation=9.452869

P(X>21)

mean=25.26842

n=19

Z=x-mean/sd/sqrt(n)

=21-25.26842/9.452869/sqrt(19)

=-1.97

P(Z>1-.97)

=P(Z<1.97)

=0.9756

ANSWER:0.9756

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