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Biostats Questions

Terms in this set (19)

Descriptive statistics are used to...
summarize data
A random sample...
is more likely to be representative of the population than any other kind of sample.
is one in which every sample of a particular size has an equal probability of being selected.
In a study of the effect of handedness on athletic ability, participants were divided into three groups: right-handed, left-handed, and ambidextrous. Athletic ability was measured on a 12-point scale. The explanatory variable is ___________________ and it is a ___________________ variable.
handedness...categorical
A study is done on Army officers that includes information on their title - e.g., Lieutenant, Captain, Major. What class of variable would be used for these data?
ordinal
The average age of piñon pine trees in the coastal mountain ranges of California was investigated by placing a 10-hectare plot randomly on a distribution map of the species in California using a computer. Researchers then recorded the location of the random plot, found it in the field, and flagged it using compass and measuring tape. They then proceeded to measure the age of every piñon pine tree within the 10-hectare plot. The average age within the plot was used to estimate the average age of the whole costal range population. Were the trees sampled randomly from this population? (And think about why or why not.)
No, Although the single plot was chosen randomly, the trees within the plot are not independent. They are more likely to be related, and more likely to have experienced similar environmental conditions, than randomly selected individuals from the population as a whole. The result is a biased sample.
What feature of an estimate-precision or accuracy- is most strongly affected when individuals differing in the variable of interest do not have an equal chance at being selected
accuracy
A study is done examining the birth weights of babies born to married and single mothers. Which of the following types of figures would best help a reader of the study see how the distribution of birth weights compare between these the two groups of mothers?
A grouped histogram
A student in Dr. Burk's Animal Behavior Lab wants to create an "activity budget" for a macaw. He spends two hours watching one individual at the zoo, recording what the bird is doing once each minute. He then wants to create a graph of the 121 data points he has for activity type. Which type of graph would be most suitable?
a simple bar graph
Two populations of peppered moths are being studied. One lives in an area where light-colored lichen covers most tree trunks, while the other lives where the darker bark of the trees is mostly exposed. Each population is sampled and the number of light and dark colored moths is recorded. Which type of graph would be the best way to present this information?
a mosaic plot
In the standard format for scientific papers, the title for a figure goes...
below the figure itself
When deciding on bin (interval) size for a histogram, the best advice it to...
try to find the combination of bin number and bin size that gives the best compromise.
For a numeric variable, the value "in the middle", with 50% of the data less than the value and 50% greater than it, is known as the ___________________.
median
The fancy-pants name statisticians use for what most people call the average is the ___________________.
mean
The interquartile range is range of the middle ______ of a numeric variable.
50%
For the following data set, what would be the correct expression of the range?

2, 2, 3, 5, 6, 8, 8, 9
7
To get the standard deviation from the variance, you would...
take the square root from the variance
Which of these equations shows how to calculate what is commonly called the "sum of squares"?
(Xi-X)^2
The value of Simpson's Index of Diversity will increase with increasing number of categories and increasing similarity of frequencies in different categories.
...
In a standard box plot (or box-and-whiskers plot], the size of the box is defined by the inter-quartile range and the line across the box is located at the median .
...
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