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23 . There are many lurking variables that could influence the observed differences in test scores. Perhaps the boys, on average, have taken more math courses than the girls, and the girls have taken more English classes than the boys. Perhaps the boys have been encouraged by their families and teachers to prepare for a career in math and science, and thus have put more effort into studying math, while the girls have been encouraged to prepare for fields like communication and psychology that are more focused on language use. A study design would have to control for these and other potential lurking variables (anything that could explain the observed difference in test scores, other than the genetic explanation) in order to draw a scientifically sound conclusion about genetic differences.

24 . To use random assignment, you would have to be able to assign people to either smoke or not smoke. Because smoking has many harmful effects, this would not be an ethical experiment. Instead, we study people who have chosen to smoke, and compare them to others who have chosen not to smoke, and try to control for the other ways those two groups may differ (lurking variables).

25 . Sources of bias include the fact that not everyone has a telephone, that cell phone numbers are often not listed in published directories, and that an individual might not be at home at the time of the phone call; all these factors make it likely that the respondents to the survey will not be representative of the population as a whole.

26 . Research subjects should not be coerced into participation, and offering extra credit in exchange for participation could be construed as coercion. In addition, this method will result in a volunteer sample, which cannot be assumed to be representative of the population as a whole.

2.1: stem-and leaf graphs (stemplots), line graphs, and bar graphs

27 . The value 740 is an outlier, because the exams were graded on a scale of 0 to 100, and 740 is far outside that range. It may be a data entry error, with the actual score being 74, so the professor should check that exam again to see what the actual score was.

28 .

Stem Leaf
6 2 4 5 5 8
7 0 2 2 4 5 5 5 6 8 8
8 1 3 3 4 5 7 8
9 2 5 8 8
10 0 0

29 . Most scores on this exam were in the range of 70–89, with a few scoring in the 60–69 range, and a few in the 90–100 range.

2.2: histograms, frequency polygons, and time series graphs

30 . R F = 7 35 = 0.2

31 . The range will be 0.5–1.5, and the central point will be 1.

32 . Range 1.5–2.5, central point 2; range 2.5–3.5, central point 3; range 3.5–4.5, central point 4; range 4.5–5.5., central point 5.

33 . The bar from 3.5 to 4.5, with a central point of 4, will be tallest; its height will be nine, because there are nine students taking four courses.

34 . The histogram is a better choice, because income is a continuous variable.

35 . A bar graph is the better choice, because this data is categorical rather than continuous.

2.3: measures of the location of the data

36 . Your daughter scored better than 80 percent of the students in her grade on math and better than 76 percent of the students in reading. Both scores are very good, and place her in the upper quartile, but her math score is slightly better in relation to her peers than her reading score.

Questions & Answers

Frequency find questions
Rimsha Reply
What is nominal variable
olusola Reply
Write short notes on, nominal variable, ordinal variable, internal variable, ratio variable.
P( /x-50/ less than or equal to 5 ) where mean =52 and Variance =25
Jay Reply
how I get the mcq
Mukesh Reply
please what is data mining
Josephine Reply
the exploration and analysis of large data to discover meaningful patterns and rules
how do we calculate the median
All Reply
f(x)=cx(1-x)^4 as x range 4rm 0<=x<=1. Can someone pls help me find d constant C. By integration only..
Akeem Reply
uses of statistics in Local Government
Saleema Reply
state road transport corporation
District statistical officer
statistical services
Please is this part of the IMT program
testing of drugs
hii 2
How about population census
Hello every one
sample survey is done by local government in each and every field.
statistics is used in almost every government organisations such as health department, economic department, census, weather forecasting fields
that's true
statistics is one of the tool that represents the falling and rising of any cases in one sheet either that is in population census whether forecast as well as economic growth
statistic is a technique, and statistics is a subject
what is business statistics
PM Reply
Probability tells you the likelihood of an event happening. ... The higher the probability, the more likely it is to happen. Probability is a number or fraction between 0 and 1. A probability of 1 means something will always happen, and a probability of 0 means something will never happen...
La Reply
Saying it's a number between zero and one means it is a fraction so you could remove "or fraction" from you definition.
wouldn't be correct to remove fractions, saying a number is justified as probabilities can also be decimals between 0 and 1.
Saying "a number" will include it being a decimal which are themselves fractions in another form.
I will simply say a probability is a number in the range zero to one, inclusive.
How to delete an entry? This last one was a pocket print.
what is probability
sky-D Reply
chance of occurrence
what is data
Muhd Reply
raw facts and figures
information of any kind
What is Statistic
ibrahim Reply
what statistical analysis can i run on growth and yield of spinach.
format of the frequency distribution table
what is pearson correlation coefficient indicates?
Statistic is the mean of the sample.
can anyone determine the value of c and the covariance and correlation for the joint probability density function Fxy(x,y)=c over the range 0<x<5,0<y,and x-1<y<x-1.
what actually is the definition of range
Chinedu Reply
I need social statistics materials
the range of a set of data is the difference between the largest and smallest values
I need more explanation about cluster sampling
write the set of old number that are greater than or equal to minutes 7 butl less than 5 in both of the set notation
Jerry Reply

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