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Unformatted text preview: STAT Bill]: Homework 8 Solutions
Instructor: Alicia Johnson 8.23 Males' ideal number of children {a} .11... = 31th; standard error = We = 1.39N854 : noes? Elf; 353; fourle '—" 1.95 (using lﬂblﬂ B}; TILCIﬁ. = tonesaid?) '— l.96*ﬂ.ﬂﬁ4? 5 ll}. [2&8 0m 95s. or is s. to 10.1263 = (2.93, 3.19) s {2.94, 3.1?) (c) We can be 95% conﬁdent that the population mean l'alls between 2.94 and 3.1T. lt' random samples ot‘size 854 were repeatedly drawn under the same conditions and 95%
conﬁdence intervals were constructed for each sample, the proportion of these intervals
that would contain the population mean would be about {195. 3.3ll Anorexia in teenage girls 3.52 9.! 9J5 9.9 [a] See Rweb output
{h} The two assumptions are that the data was obtained by randomization and that there is
an approximately normal population distribution. Both assumptions should hold here. {c} Sec Rweh output
(d) x... = 129; standard error '= shin ~'—' '1. 13h“? — 114 dl'= to; Iubrm'tt = 2.12 {using tahlc B); m.o.c. = a. noise} 112*].7'4 = 3.69
Our 95% Cl is "3.29 i see = (see, 1&93) {e} See chb output
(i) The true mean weight change is likely positive because no negative scores fall in the conlidence interval. The true mean weight change could also he very small because the
lower end point of 3.ft is near III. (g) lncreasing the sample size a could narrow the Cl. Decreasing the confidence level (For example. to sets) could also narrow the Cl. Income of Native Americans
We guess that the range ol'a bellshaped distribution is about as. One sixth ot‘thc range of menus is 20sec. a good guess for the standard deviation.
n = {o‘z‘E‘y'm’ = {smoooirasrsiynooe’ = 2,e52.2s; round up to 2.1553. Iowa GPA Ho: Ill = H..: p at sea In the above hypotheses, Ho is the notation for
alternative hypothesis, and ,a is the parameter,
we‘re hypothesizing. the null hypothesis, H. is the notation for the
the mean GPA ot‘ the population, about which Examples of hypotheses Psychic
The null hypothesis is that the psychic will predict the outcome of the roll ot'a die in another room we ot‘the time, and the alternative hypothesis is that the psychic will predict the outcome more than no of the time.
Ho: p =1re and H..: p is Ito 9.111 Believe in astrology?
Hi] refers to the null hypothesis, and He refers to the alternative hypothesis; p refers to the true pl'ﬂbabilitji of a correct guess.
Hep: 'faand Hep} 'fq Rweh Output for 3.30 Rweh:) poetseripttfile= "ftmp!Reut.23391.ps"i Rweh:h x < read.tablet"!tmprdete.Eﬂial.dete”. heeder=T1
Rweh:> attachixi Rweh:e nemeeixt [1] “change” Hweh:> Rweh:e Rweb:: etemtchangei The decimal point ie 1 digitiei to the r1ght of the   543  0456399
 111334
 2 Rueb:> meantchangei [1] 3.294113 Rweb:> adichanqei [1] 3.18300? Rweb:e t.teetix=ehenqe. een£.1eve1=0.95. e1ternetive="twe.aided"i One Sample tteet data: change t = 4.1359. df = 15. puelue = ﬂ.ﬂﬂO69T4
alternative hypothesis: true mean is net equal tn 0
95 percent confidence interval: 3.600956 10.9572TB eemple estimates:
mean of x 3.294115 ...
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 Spring '09
 WANG,ZHAN

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