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Stat 221  Quiz 1 1) For the following research issues:
— Identify the “observational units” in the study
 Identify the variable of interest in the study (make sure you state them as variables)  Identify the variable as quantitative or categorical
If you think the measurement is ambiguous, explain why. (a) A comparison of injury rates for several high school spurts showed that ice hockey was the
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(b) A new Gallup poll reveals that about onefourth of the country can speak a language
other than English well enough to hold a conversation.
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provides for governmentsponsored insurance for nursing home care. You report that 1128 letters
have been received on the issue, of which 871 Oppose the legislation. The representative says
“I’m surprised that most of my constituents oppose the bill, I thought it would be quite popular.”
In response to this conclusion, comment on a possible bias, if any, regarding voter opinion of the b111, and the direction of the bias. VOW k QP,WLL.C1,L LA agﬁwgg r 996%
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Names: . w" ' " Vw‘) Stat 221 QuizS h . . "‘ You may use your notes and tables. 1) The average number of days spent in a North Carolina hospital for a coronary bypass
in 1992 was 9 days and the standard deviation was 3 days. Suppose that the duration of
stays is normally distributed. (a) What is the probability that 10 randomly selected patients will have an average stay '
longer than 11 days? Include a well—labeled sketch of the sampling distribution of
average lengths of stay. Vt} 3D 4am, bM pop. 18 norm/Lax! .ﬁgjL ‘4'?"  i\'\“'\§>\r X {mini 0L1tﬁl€ trawl“ l’hﬂﬂ WUU bm/
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(b) How would this probab1lity d1ffer (larger, smaller, or the same) 1f you calculated the
probability that an individual had to stay longer than 9.5 days? (You should not calculate Okay Sf
this probability.) Explain why this makes sense intuitively. The ovobaloukt'bj would log \ﬂmjm, Thu? modiﬁes §UM6 mﬂdtuéhj (Maude We value)
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Stat 221 — Quiz 3 1 ’ L“ 1) Suppose an advertisement reported that the mean weight loss after using a certain
exercise machine for 2 months was 10 pounds. You investigate further and discover that
the median weight loss was 3 pounds.
(a) Explain whether it is most likely that the weight losses were skewed to right (positive
skew), skewed to the left (negative skew) or symmetric. / /""\\ It \.‘_ _ ﬁsngwecw "mi Uririj , ye ‘DeobLC__——~—”“”"j * —""‘ r. l onvgrtbékf MIST kl! i/K (TuMUMLTE; inf} V\JC"‘..C/1PUTJ 3”“‘u L"; ‘5‘!" “writ?
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at ’(ﬁCU ‘1. RR litii, {,‘jJMLi/L "‘ l :9 I = / 1 (b) As a consumer trying to decide whether or not to buy this exercise machine, would it
have been more useful to you for the company to give you the mean or the median? ~ Explain. “Jr/[M pncdmiL Lygfijﬁf; (1 Wm; me; an 941+ {O { i/lv’lCLlLC’S H SUCH/l statCt @fCWWLC my; ‘itu lfx’c’TiﬂUSE" . rte a? CWEWM '\ f /
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. u _ 2) The descriptive statistics below represent the scores on a test of “political awareness”
achieved by a sample of college students. Variable N Mean Median TrMean StDev SE Mean
score 500 86.60 58.57 75.97_ 90.30 4.04
Variable Minimum Maximum Q1 Q3
score 1.00 658.00 24.61 120.69
(a) The middle 50% of the data is between what two values? .\
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(b) Use the 1.5iqr criterion to determine if there are any mild outliers in these data.
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Stat 221 — Quiz 4 D! 1) Suppose that 40% of those eligible for jury duty in a certain community are senior
citizens over 65 years of age. (a) Is this number 40% a parameter or a statistic? Explain. ﬁrm/Wei. beam WE WW' ‘5 6k waW[gﬁg a?) 0L. Jlr101'a3m pLQ, (b) If 12person juries are selected as simple random samples from the population of ‘
those in this community eligible for jury service, would every jury contain 4 senior.  ' —r _. aranE = __.=
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500 randomly selected 12—person juries from this population with 40% senior citizens. ‘ 1,13“: ‘ R
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(c) Give each axis an appropriate label.
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(d) Explain what is represented by each dot in the above graph. 1 . ‘ .
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citizens would be more sympathetic to her than younger jurors would be. Suppose that the jury selected to hear her case contains only two senior citizens. Would you
Say this is a common or an unusual outcome? Explain your answer. 77415 {601}? arm) WLLLSE/Lou because mjwwj urn/aw be l {w}! Ctr/056V] and % “fl/U0 SMLoE/ 0&1ng '\‘"
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Stat 221  Quiz 2 ﬂ 1) For the following research issues indicate whether you would use an observational study
(including survey) or an experiment to answer the question and brieﬂy explain why (include why
the other type of study is not appropriate). (3.) Does a high level of salt in the diet lead to higher levels of blood pressure? i .21)"; 8X ‘IWT ﬂ} ‘bvt EDI/Lid Halli “fl/Lt (swpa) sea/1c.
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(b) Do states with more liberal concealed weapons laws have lower crime rates than states with
more conservative concealed weapons laws? DbgﬁV’VQﬂDﬂWi “‘“’ it would \x appropvicdre tin owed/Vt: the,
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WWW or ﬁrms law's M lcbeval 01/ nor. ,Q;T\J;;—,,a ‘71. m, 2) The following were some of the variables I measured on you with the WebCT survey
(a) your heights ‘ (b) number of siblings (c) amount paid for your last haircut (d) amount of change in your pockets (e) your guesses of my age For each variable, do you think the shape will be symmetric, skewed to the left (negative skew)
or skewed to the right (positive skew)? Feel free to defend your choice and/or sketch a graph. (a) S mwmj’vi L, / 5
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Stat 221 — Quiz 6 332/ For this quiz, you may use your books, notes, and one other person. Turn in one quiz for both of you. We have learned the following procedures
(a) One sample proportion z—test (b) One sample proportion zinterval
(c) One sample mean ttest (d) One sample mean tinterval
(e) Two sample proportions ztest (f) Two sample proportions zinterval
(g) Two sample means ttest (h) Two sample means tinterval (i) Chisquare test for independence
(j) ANOVA test for several means 1) For each situation below, identify the appropriate inferential procedure from the list above,
and if a test of signiﬁcance clearly state Ho and Ha. If you think there is any doubt in your
choice, explain your reasoning. (a) A university anticipates that next year there will be a need to house 47% of its
undergraduate students. The student newspaper conducts a random sample of 50 students
who claim to be returning next year and wants to know if there is signiﬁcant evidence that
the university should increase their estimate of the overall proportion who need housing. is (WWj WVW C’s/ﬂak
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\Sb L\ l’lll .1 ‘l (b) Three major radio stations service a large metropolitan area. An independent marketing
ﬁrm classiﬁes listeners as “young” and “mature” based on their age. The ﬁrm surveys one
hundred ratio listeners and asks which station they listen to most. They want to know if there
is a relationship between the listener’s maturity level and which station they prefer.  ' ‘ W Lye, HAW 0‘
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‘/ WM ctr Sam’er ' (c) There are approximately 30,000 companies that are members of a charitable collaborative
across the entire country. A random sample of 250 of these companies is taken and it is found
that 210 of the CEO's and 8410 of the 15,000 junior executives hold at least a master's
degree. You are asked to estimate how much higher the population proportion of CEO’s
with a master’s degree is than the population proportion of junior executives. ' Sf M' ‘ H bun/W knaStoVS C‘E/O‘S
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Stat 221  Quiz 5 You may use your notes and tables. 1) The average number of days spent in a North Carolina hospital for a coronary bypass
in 1992 was 9 days and the standard deviation was 3 days. Suppose that the duration of
stays is normally distributed. (a) What is the probability that 10 randomly selected patients will have an average stay
longer than 11 days? Include a well—labeled sketch of the sampling distribution of
average lengths of stay. (b) How would this probability differ (larger, smaller, or the same) if you calculated the
probability that an individual had to stay longer than 9.5 days? (You should not calculate
this probability.) Explain why this makes sense intuitively. ...
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