~azc:
CL ~
~
c~th c>4-
L4%tD
5CCV%~~e4-\f~
o~ ~
~°
~c
L wa
oLoo~
(~D&4~~ ~Ucr)
&
~
cetop~4)
vcs
WAs
~JJr
t
t
S
cLtSt’
k-s
L~ ~
54v’~~~ crt~
≤&~~
v29
~cccLck
I4~
(su~
S~cL ~
S
tL!;j
t~zi4e~
(CL)
(~
sa~ak
~6
~~\4~V~U
~+a~
~trC
o4-~*v~es.
4cJ~c
I)
a~
S uictcfl~iC
+zai~A- ~
&~ts
S
c~k~?
(&c%%4)
S
~OO
40
(LO
(b~
~
pLoce
~
~
~
(c) ~
of
~
~
~
cccv~1o&
Lgh4~tt~co-Q
S
O J~°~
G
~
s ~fv~p~tL2
)
Sa~p~
wit
~
~
~)
of
~g~v~OvtfS
~
41—4€
4
24
Sf-&5 +~
~
a
~
~
9~
o~
s I J&cs)
s+ax+’~~
~
~s ~
~ ~
~o
I ~
~
Q~i~cA-
°~‘
~
9 ~9
}
0A
S
~
I fl~
S~
fA~Ot~O
S
g (c≠c4)
stLyt
S
cótd~
v~
F
~
~ caS ~
~
40
LAi~
-
~ CCtL~y~
~
)
~
orv&r
o~
s a~r~~p& ~
—
I,
.A~k a sIiiipic of college students these two
How happ~ are
~
o
ycTh J4s
LItiestiolls:
u with your life in general?” (Ansu ers n
i
scale at I to
Ho” nianv dates did you have last month
The correlation between answers is r = —0.012 when i ked in this order. Lt appear’
that dating has little to do with happiness. Reverse the rdcr ot the qUestions, however,
and r = 0.66. Asking a question that brings dating to mind makes dating success a hi~
factor in happiness.
rtu~s
692
TABLE S
TABLES
Random digits
LINE
101
102
(03
04
105
106
107
108
109
110
III
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
19223
73676
45467
52711
95592
68417
82739
60940
47(50
71709
38889
94007
35013
57890
72024
05756
99400
77558
93074
69971
15529
20807
17868
2871$
0(927
00095
60227
91481
72765
47511
24943
36009
19365
15412
39638
38448
81486
59636
62568
45149
61041
14459
38167
73190
95857
35476
71487
13873
54580
71035
96746
96927
43909
15689
36759
69051
05007
68732
45740
27816
66925
08421
53645
66831
55588
12975
96767
72829
88565
62964
19687
37609
54973
00694
71546
07511
48789
69487
$8804
70206
32992
77684
26056
98532
32533
07118
55972
09984
81598
81507
09001
12149
19931
99477
14227
58984
64817
16632
55259
41807
78416
55658
44753
66812
68908
99404
13258
35964
50232
42628
88145
12633
59057
86278
05977
05233
88915
18338
60513
04634
40325
75730
94322
31424
62183
04470
87664
39421
29077
95052
27102
43367
37823
36809
25330
06565
68288
87174
81194
84292
65561
18329
39100
77377
61421
40772
70708
13048
23822
97892
17797
83083
57857
66967
88737
19664
53946
41267
24697
09297
71197
03699
66280
24709
80371
70632
29669
92099
65850
14863
90908
56027
49497
71868
74192
64359
14374
22913
09517
14873
08796
33302
21337
78458
28744
47836
21558
41098
45144
96012
63408
49376
69453
95806
83401
74351
65441
68743
16853
95034
96409
27754
2863
40011
60779
85089
81676
61790
85453
39364
00412
19352
71080
038(9
73698
65103
23417
84407
58806
04266
61683
75592
55892
72719
(8442
77567
40085
13352
18638
84534
04197
43165
07051
35213
11206
75592
12609
47781
43563
72321
94591
77919
61762
46109
09931
60705
47500
20903
72460
84569
12531
42648
29485
85848
53791
57067
55300
90656
46816
42006
71238
73089
22553
56202
14526
62253
26185
90785
66979
35435
47052
75186
33063
96758
351(9
88741
16925
49367
54303
06489
85576
93739
93623
37741
19876
08563
15373
33586
56934
81940
65(94
44575
16953
59505
02150
02384
84552
62371
27601
79367
42544
82425
82226
48767
(7297
50211
94383
87964
83485
76688
27649
8489$
11486
02938
31893
50490
41448
65956
98624
43742
62224
87136
41842
276(1
62103
48409
85117
81982
00795
87201
45195
31685
18132
04312
87151
79140
98481
79177
48394
00360
50842
24870
88604
69680
43163
90597
19909
22725
45403
32337
82853
36290
90056
52573
59335
47487
14893
[8883
41979
08708
39950
45785
11776
709(5
32592
61181
75532
86382
84826
11937
51025
95761
81868
91596
39244
41903
36071
87209
08727
97245
96565
97150
09547
68508
31260
92454
14592
06928
51719
02428
53372
04178
12724
00900
58636
93600
67181
53340
88692
03316
\J0CJ0
4— ~-&.-eL5c.crfS
O~DSaWe3
i-c
v’~~-~ £4J26! -S
£~3Jo
ii
N
S~Q~tr~tia v’~°1-°-s sav~c
4- ,~A.n_o~cLJJ_e ~ r&S
Is
r~Sfo~t
t___~
~
Tc.r
~
vet9raWS
cu~
¼~ ~
C- VCS
N
@~pe4rL~~zt:
~rcQ4n
cc~v~at0+ L24~
aces c~’~s
-
an~S
nu~L~~ ~
*
j-ê~fuJfl’
btc9-a~2~c
c~&u’%aU-y
(,rc~k,
C
a~ “-~r~
~‘+
L’~J JALrkfl~
~~kLes.
Lc tc-~ a%penn&
04- ~4J%k~’~
M4~
A,
~v~t
sJojcct
CA—’
6e
I,
%1A-0J4
~
5 cr~~°
~cSak res1fl~-
3-
~yptrLr~’e~
4
44as
flJ≥Q~ J~e,v~ ~ V~’~~w
≤~~L2~eck ~c
Mt~0
C2xp I
Ti oUo~3
-
—~
&~ r’-~
~
~
asflr-n’-~~
~
Its—
cu-r-c.
(z)
~LrC
~
e,~&s
Bos~c
0ç
~
S~c+~c~O
arfi
ca~-°~
(~~C
D~s~-v~ e4L ~cpzrct~aJEs
~4 9LLri0~ vojnaM-’~s
~ ~c)
~
(~)
~
&cs~)
V&’
S
4c 6t
a
~
3
I,
~
V~i
4
v~
(I~ ~
Mt~0
-~
~
[
J
K
K
2—
Cell phones and brain cancer. A study of cell phones and the risk of brain cancer
looked at a group of 469 people who have brain cancer. The investigators matched
each cancer patient with a person of the same sex, age, and race “ho did not have
brain cancer, then asked about use of cell phones.2 Result: Our data suggest that use
ofhandheld cellular telephones is not associated with risk of brain cancer.” Is this an
observational study or an experiment? Why? What are the explanat r~ md response
variables?
How long did I work? A psychologist wants to know ii the difficulty of a task influ
ences our estimate of how Long we spend working at it. She designs two sets of nia:es
that subjects can ~sork through on a computer. One set has easy mazes anti the other
has hard mazes. Subjects work until told to stop (after 6 minutes, hut subjects do not
know this). They are then asked to estimate how long they worked. The psychologist
has 30 students available to serve as subjects.
(a)
Describe the design of a completely randomized experiment to learn the elfect
oldifhculty on estimated time.
(b)
Describe the design of a matched pairs experiment using the same 30 subjects.
jflt
caD
9
~3
(c~~v’*~
Attitudes toward homeless people. Negative altitudes toward poor people are
common. Are attitudes more negative when a person is homeless? To find out, read
to subjects a description of a poor person. There are two versions. One begins
Jim is a 30-year-old single man. He is currently living in a small single-room
apartment.
The other description begins
Jim is a 30-year-old single man. He is currently homeless and jives in a shelter
for homeless people.
Alter reading the description, ask subjects what they believe about Jim and what
they think should be done to help him. The subjects are 544 adults Lnterviewed by
telephone)2 Outline the design of this experiment.
Experimental design. The clinical trial was a completely randomized experiment
that asstgned 240 patients at random among 4 treatments as follows:
Antibiotic
pill
Placebo
pill
53
60
64
63
Sterotd spray
Placebo spray
(a)
Outline the design of the experiment.
(b)
How will you label the 240 subjects?
(c)
Explain briefly how you would do the random assignment of patients to treat
ments. Assign the first 5 patients who will receive the first treatment.
~dThD
S
i (cc~4)
4c~d
aYarv~~r&~(
Cell phones and driving
Does talking on a hands-free cell phone distract dri~ers? Undergraduate students
“drove” in a high-fidelity driving stmulator equipped with a hands free cell phone. Thc
car ahead brakes: ho” quickly does the subject react? Let’s compare two designs for this
experiment. There are 40 student subjects available.
In a complet ly randomized design, aLl 40 subjects are assigned at random, 20 to simply
drive and the other 20 t talk on the cell phone while driving. In the matched pairs design
that was actually used, all subjects drive both with and without using the cell phone.
The two drives are on separate days to reduce carryover effects. The order of the two
treatments is assigned at random: 20 subjects are chosen to drive first with the phone,
and the remaining 20 drive first without the phone.8
Some subjects naturally react faster than others. The completely randomized design
relies on chance to distribute the faster subjects roughly evenly between the two groups.
The matched pairs design compares each subject’s reaction time wtth nd without the
cell phone. This makes it easi≥t to see the effects of using the phone.