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Unformatted text preview: STAT 221, Fall 2005
Exam 1 CalifomiaPolytechnic State University, San Luis Obispo ) w
.J. _i i, - 7J4 w. Name! 4r , True/False, Multiple Choice, Fill in the Blank (1-3 Pts Each} 1. Ln.) Groundwater concentration of nitrogen was measured at several sites, some "near" agricultural land, others
“not near" agricultural land. Sites were selected in 8 different counties in California. Many measurements were obtained at each site over 5 years. Match the graphs that would be most useful for each of the
following questions. 1. How has the nitrogen concentration changed over the 5 years of study at
one of the sites in articular? 3. For each site, consider averaging the nitrogen measurements over all 5
years. Is there a relationship between a site's average nitrogen level and
its distance to the nearest aricultural ﬁeld. 4. Do nitrogen concentrations at a particular Site roughly follow a normal DE high in terms of nitrogen concentration. Is there a difference in the
proportion of sites that are low, medium, and high in nitrogen
concentration between sites that are near versus not near agricultural
land? Which of the following cooefficients indicates the strongest linear association? Circle one.
In : a; —0.25 @080 d. 0.34 [f the estimated least squares line is given by j; = 35 -—12x , what is the most reasonable correlation coefﬁcient for this data? 'rcle one. ’i
a. 12 @42 d. 0.50 eBay has a database containing the dollar amounts of about 200,000 sales made using eBay yesterday. To summarize the distribution of these sales which f the following 5. . hs would be most useful? Circle one.
a. Histogram b. Stemplot c. Boxplot @a) and (b) (c) f. All of the above Suppose the time that a table of 4 customers stays for dinner at a certain restaurant follows a normal model with mean 32 minutes and standard deviation 6 minutes. Approximately, in what range would you expect
the central 95% of all dining times to be? , L a. etween 26 and 38 minutes \0 ’2 Z 515' V J etween 20 and 44 minutes i c. Between 14 and 50 minutes d. More information is needed True or a . A high leverage point is any point with a large residual. var 7. r‘ Tru or A correlation coefﬁcrent close to +/- 1 indicates that there IS causal relationship between the
o ia es. .wr False: If height and weight have a correlation of 0.75, then people with heights 1 standard deviation a e the mean will tend to have weights 0.75 standard deviations above the mean. ﬁTmle}or normal probability plot is used to compute probabilities for variables that follow the normal u- lO. True or Falseii The standard deviation is not easily affected by outliers. Page 1 of 4 C. Segmented bar graph
or several pie-charts ' Pf'l'implot . 5. Suppose there is reasonable way to categorize a site as low, medium, or C v . Scatterplot California Polytechnic State University, San Luis Obispo l4. (5 Pts) Consider the following boxplot. WW quarliLt
marsh Income 7 3.. Indicate on the Income axis of the graph where you think the median income is.
b. Indicate on the Income axis of the graph where you think the upper quartile is.
c. Which of the following best describes the shape of this distribution? Circle one.
I. Symnietric @kewed to the right 3. Skewed to the left 4. U ' cm 5. Shape cannot be determined
d. Will the mean income likely be larger or smaller than the median income? Circle one or Smaller. 15. (8 Pts) Suppose the live weight at slaughter of an angus steer follows a normal model with mean weight
450 kg and standard deviation 25 kg. I:
m 337% 9>\ .55 a. Find the percentage of these steers that weigh above 480 kg at slaughter.
‘60 r as 14?? t 3% 9o?" L} Rig-"Lat; - UH _ ] W1 V10 1? <7” , z: . « W 32$? selﬁsh «EVEN ﬁts-«00mg / r “is. St; ﬁvgasl; g9; zlsZ ﬂ b. What is the cutoff value for the lowest 20% of the weights at slaughter. axlwét‘” V
Z. 2, ‘i Kat’s/m} 9D l
“I 0 :- 4 Page 3 of4 "
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This homework help was uploaded on 02/13/2008 for the course STAT 221 taught by Professor Lund during the Fall '05 term at Cal Poly.
- Fall '05