Department

StatisticsCourse Code

STATS 13Professor

Tsiang, MikeLecture

1This

**preview**shows pages 1-2. to view the full**7 pages of the document.**Discussion Notes!

!

Midterm Review!

suppose hypothesis is μ = .25 and μ < .25, which standardized statistic = strongest evidence against the null hypothesis and •

for the alternative!

t= -1.80 bc highest absolute value and bc its less than so it needs negative!◦

mean cost of wedding is $698. in a sample of 40 weddings, it was found the average cost of ﬂowers was $734 with a •

standard deviation of $102. with a 95% conﬁdence interval for the mean cost of a wedding is $701 to $767!

what is the mean cost or a wedding based on the conﬁdence interval with an α level of .05!◦

1 - α means 95% conﬁdence interval!‣

answer: the mean cost of ﬂowers for a wedding in the US is more than $698!‣

conﬁdence intervals!◦

what is the best interpretation of the 95% conﬁdence interval!◦

if we were to do this survey a great many times, about 95% of the resulting conﬁdence intervals would include the ‣

mean cost of ﬂowers for all weddings in the US!

choose the statement the best describes what is meant when we say the sample mean is unbiased when estimating the •

population mean!

on av the mean of the expected is = to the population!◦

on average, the sample mean is the same as the population!◦

ann perkins on time ambulance response within 3 minutes, overall proportion of on time responses in the city as a whole is .•

45 π = .45 π < .45!

suppose her sample is 50 but only 20 are on time!◦

to carry out a simulation based test, ann collects red and blue poker chips and echoes that the red chips represent on ◦

time response and blue represents not on time responses. she plans to put a large number of poker chips and takes out

50 random chips. what percentage of the chips in the box should be blue?!

on time 45 so red = 45 blue should be 55%!‣

according to the centers for disease control, about 18% of adolescents age 12-18 are obese. supposed we take a random •

sample of 30 adlescents and ﬁnd the proportion in our sample who are obese. !

suppose we make a dot plot of the sample proportions. would the do plot be a visualization of the population ◦

distribution, distribution of the sample, or sampling distribution!

sampling distribution!‣

if instead of 30 we took a sample of 300, how would the distribution as visualized by the dot plot change !◦

as we increase sample size, we get closer to the normal disitrbuion !‣

the spread will decrease!‣

a. the center would be about the same but the spread would be smaller and the shape would be close to the ‣

normal distribution !

JJ lips come over of JJ diner in pawnee indiana wants to make a new waﬄe that is made with batter that has been infused •

with whipped cream. he makes 800 waﬄes and some unknown proportion of them were made with the new whipped cream

infused waﬄe batter. each waﬄe was made individually so no two waﬄe was stuck together. supposed leslie orders 30

waﬄes from JJ diner. jj randomly selects 30 waﬄes from the 800 and she notes that 90% of them were infused with

whipped cream!

she wants to use the empirical rule but one of the validity conditions is not satisﬁed!◦

sample is not random X states that it is random!‣

sample is not large enough ** this is the answer!‣

bc she needs to meet the condition of 10 successes and 10 failures but her # of successes is .9 (30( = 27 but •

number of failures is 3!

population not large enough X n > 20 // 20*30 = 600 < 800!‣

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

Only pages 1-2 are available for preview. Some parts have been intentionally blurred.

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

tip code but label for category

not absolute scale

sample mean depends on how you take sample

mean may vary alot

SD of sample dist fpop standard deviation

NNLM

on average sample mean pop mean

95 Cont Int

Want Smaller MoEW

lo tr in coutid

changing It changes confid

larger nwill go down so cout stays

same bit MOE smaller

just 9larger random sample

###### You're Reading a Preview

Unlock to view full version