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**Unformatted text preview: **Quiz 01.doc Statistics 130, Fall 2000 _ Answer questions brieﬂy in the space provided. Thinking carefully before writing pays oft".f study comparing the length of colds for those who take Echinacea and those who don‘t. Each particip - was asked to keep track of the length (in days) of each cold they had October through March. Of the 599 '
people who did not take Echinacea the average length of colds was 1.8 days. Of the 215 people who voluntarily took Echinacea to prevent colds the average length of colds was only 1.5. This diﬁ'erence is
large enough that it could not have occurred by chance alone. 1. Are there any extraneous differences (or confounding factors) that may make this study difﬁcult to
evaluate? Give one or two examples of such possible differences. - ._..I v _ _ ' , ,,, ‘ . - 7
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would you think it worthwhile, even if effective? Why or why not? «rye-amt It Wat 196 WWW beam
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Quiz 02.doc Statistics 130, Fall 2000 Rein Answer questions brieﬂy in the space provided. Thinking carefully before writing pays off! 1. Airlines compute the percentage of ﬂights that are on time to be the percentage that arrive no later than 15 minutes after their scheduled arrival time.
a. Is ' a valid measure of on-time perfonnance? Explain. 09mm M a yaw/at 03 on}
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b. Isthisareliable measure? Explain. ‘ I I ’W’WWM a WW6 mam a! /s““ nut/tea; 7%: W _
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4% mﬁ/m/ﬂm‘ mﬂm girls saga/mam 45m. 2. If we conduct a study to determine the relationship (if any) etw city of orig: , scheduled
departure time and whether the ﬂight is arr-time or not, identify each variable as explanatory or response. 61+? 0? m h 'zxpfmayhmj, .
Mama own/marinate “ exp/mainly” Mahme ﬂ/l/lm‘W 3. Identify the method of sampling if we sample ﬂights ﬁor this study so that each of the 8 major
airlines (United, American, Delta, USAif, Southwest, Continental, Northwest and Alaska) has exactly 200 ﬂights in the dataset. [Lt/4ain Jim/2de @MW/qdé. 1 / ' n K“ t r. _/|
Quiz 03.doc Statistics 130, F all 2000 Rein Answer the following True/False questions for one point each. 1. E 'ﬁe’standard deviation of a dataset is always smaller than the mean. True .
2. m A dataset with a skew-left histogram has a mean that is smaller than the median. ﬁll-V101 l’: WiOl/C _ , 6.0mm! mph
3. T HA 5 A dataset with a symmetrical histogram has about half the data values above the
mean and about half below the mean. 4. ELM Eutliers inﬂuence the mean. 5.T% FOutliers inﬂuence the median. 6. iOutliers inﬂuence the quartiles. 7. Fa lSC If the standard deviation of a dataset is 0, we can conclude that all the values in the dataset are zeroes
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$6 5 0 4m came a: 8. ' I E M CAbout 2/3 of the area in a normal distribution is in the mean plus or minus one standard deviation range. NE: ( (if; 2M ,-~ "" 4+
. v 9:7 mm W 7590 . .
9. T r If we know that salarie bf wbrkers 1n the state of Callforma have mean level $40,000 and standard deviation $25,000, we can conclude that about 2/3 of California workers v sal ' in 11% $15,000 to $6 00 r ge.
. W W
mwaﬁw N v~ ’lO '6 H0 (96 010 10.. W C If we believe that the birthweights of full-term infants follows a normal
distribution with mean 8 pounds and standard deviation 1.5 pounds, we can conclude that / 1 Quiz 06.doc Statistics 130, Fall 2000 Indicate whether the following four statements are True or False for two points each. I. If two events are independent, that means that they cannot simultaneously occur. m9?” " A Mr: OPP/Mbﬂb’lllg 13 that \l‘ L .W
anM+: PM ml warm; t? W WM MWVK,W
C-A/mmﬁmwmem 0cm. M If the chance that I roll a six on a die is not in
rolling a six on the first roll is independent 0 true 2. ﬂuenced by whether the previous roll was a six, we can say that f rolling a six on the second. 3. If there are only two possible outcomes to an experiment, because the sum of the probabilities must be 100%. Was/Wu: 0th
+0 {00% , 171% the chance that each one occurs is exactly 50% mam deter/2% WM) mm hash lace
9070‘ 170K exam/(ems (me could have a 70% mama
ugh Mal mm: (mm have A 519% aha/me. Eighty percent of Cal Poly students were in the top 25%
students are no more or no less likely to he in the top 2
Poly students. Using this information, answer the fol] of their High School graduating class and male Cal Poly
5% of their High School graduating class than female Cal
owing questions for 2 points each. 4. What is the chance that a randomly chosen Cal Poly student is a female who graduated in the top 25% of her
High School class? +0 sot WW3 = 263% aft
eta-Em WW’CZ:59"’v
Eb: Pl malt) — 60/. “Female-é m hwy/a?) = WPer 5): P(A)r?(s) 1-.4000—7 5. What is the chance that the student I select 15 a male who dld not graduate in the top 25% ofhls High School
class?
I * Plno’rAVPM) PLmMa)‘ .50
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Quiz 07.doc Statistics 130, Fall % close sample proportions are to the population proportion. What is an equation that would allow me to calculate this standard deviation?
6 .0, r p( l e ) Fl 2. Suppose you take a simple random sample of Cal Poly students and ask each his GPA. Suppose also that the
mean GPA of students is 2.89 and that the standard deviation of student GPAs is 058. Is it likely that the mean
of 100 randomly chosen GPAs would be 3.00 or higher? Explain. X12955? so»: 058- \ HUI/HMS Medal not he “Wilt/f too'AZaUJ D€CtUAA£-lnlhttjtult OPgﬂinuowx
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dLMVaMA. 3. Suppose you take a simple random sample of Cal Poly students ask each his age. Suppose also that the mean age of students is 21.3 and that the standard deviation of s is 1.68. prossible, determine a range of i 1
age values would contain about 95% of the sample means we could see for samples of size 100. Ifnot possible, ’ (a g
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wﬁwi 20% 3th 21. {05b 4. If, in fact, 9% of Cal Poly students are vegetan' and we are to sample 250 Poly students at random, what are
the expected value and the standard deviation of the percentage of vegetarians in the sample? 11/02/00 ...

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