AP STATISTICS VOCABULARY
bimodal
a distribution having two local maxima ?: Select the two most highest points in this bimodal graph
variance
the expectation of the squared deviation of a random variable from its mean ?: You have found the following ages (in years) of all 66 lizards at your local zoo: 1, 2, 2, 1,3,31,2,2,1,3,3 What is the average age of the lizards at your zoo? What is the variance? Round your answers to the nearest tenth.
degrees of freedom
the number of degrees of freedom is the number of values in the final calculation of a statistic that are free to vary. ?: Question 1: Find the degree of freedom for given sequence: x = 2, 8, 3, 6, 4, 2, 9, 5
stratified
the process of dividing members of the population into homogeneous subgroups before sampling ?: A school has 650 students. Each student studies one of Greek or Spanish or German or French. The table shows the number of students who study each of these languages. An inspector wants to look at the work of a stratified sample of 70 of these students. Find the number of students studying each of these languages that should be in the sample.
inference
the theory, methods, and practice of forming judgments about the parameters of a population and the reliability of statistical relationships, typically on the basis of random sampling. ?: Based on the data, what is the most reasonable estimate for the number of Bounce Club members whose favorite type of music is jazz music?
Undercoverage
a type of selection bias . It occurs when some members of the population are inadequately represented in the sample. ?: A classic example of undercoverage is the Literary Digest voter survey, which predicted that Alfred Landon would beat Franklin Roosevelt in the 1936 presidential election. The survey sample suffered from undercoverage of low-income voters, who tended to be Democrats.
standard error
estimated standard deviation of the statistic ?:
Replication
experimental design principle. Use enough experimental units in each group so that any differences in the effects of the treatments can be distinguished from chance differences between the groups ?: Randomly selecting two individuals from a group of four and applying a treatment with "great success" generally will not impress the public or convince anyone of the effectiveness of the treatment.
empirical rule
The empirical rule states that for a normal distribution, nearly all of the data will fall within three standard deviations of the mean. ?: The lifespans of lions in a particular zoo are normally distributed. The average lion lives 12.512.5 years; the standard deviation is 2.42.4 years. Use the empirical rule (68-95-99.7\%)(68−95−99.7%) to estimate the probability of a lion living less than 10.110.1 years.
disjoint
Two events are mutually exclusive if they cannot occur at the same time. Another word that means mutually exclusive is disjoint. If two events are disjoint, then the probability of them both occurring at the same time is 0.
statistic
a numerical measurement describing some characteristic of a sample ?:
xbar
mean of a sample ?:
SUCS
Shape, Unusual Features, Center, Spread ?: Describe the possible SUCS for the graph
sample space
The set of all possible outcomes of a chance process. ?: A teenage girl is trying to put together her fall outfits. Each outfit consists of one top, one bottom and one accessory. The list below shows the pieces of clothing that she has in her closet. TOPS - sweater, hoodie, long-sleeved blouse, polo shirt BOTTOMS - pants, skirt ACCESSORIES - scarf, headband, beret How many different outfits are in the sample space AND what proportion of all the different outfits have the hoodie as the top?
parameter
a number that describes some characteristic of the population ?: A researcher wants to estimate the average height of women aged 20 years or older. From a simple random sample of 45 women, the researcher obtains a sample mean height of 63.9 inches.
nonresponse
occurs when an individual chosen for the sample cannot be contacted or refuses to participate ?:Which of the following statements are true? I. Random sampling is a good way to reduce response bias. II. To guard against bias from undercoverage, use a convenience sample. III. Increasing the sample size tends to reduce survey bias. IV. To guard against nonresponse bias, use a mail-in survey.
invnorm
probability distribution function that will find the precise value at a given percent based upon the mean and standard deviation. ?:Heights are generally found to be normally distributed. Assume that the average adult female height is 65.5 inches with a standard deviation of 3 inches. (a) What height do 90% of women fall below? (b) What height do 60% of women measure above? (c) What two heights, symmetric about the mean, contain 80% of all women's heights?
central limit theorem
states that the sampling distribution of the mean of any independent, random variable will be normal or nearly normal, if the sample size is large enough. ?:The average GPA scored by a a class is $4.91$ and standard deviation is $0.72$. For a sample of $20$ students, find the z-score that the average is above $5$.
p-hat
we use Phat to designate the proportion in the sample. ?: Approximately 60% of all part-time college students in the United States are female. (In other words, the population proportion of females among part-time college students is p = 0.6.) What would you expect to see in terms of the behavior of a sample proportion of females (p-hat) if random samples of size 100 were taken from the population of all part-time college students?
confounding
when the experimental controls do not allow the experimenter to reasonably eliminate plausible alternative explanations for an observed relationship between independent and dependent variables. ?: A confounding variable can have a hidden effect on your experiment's outcome.
