Week 2 Flashcards

Question

What is interquartile range?

Answer 1

the difference between the first and third quartiles

Answer 2

the composition depends on all the data. the larger the variance, the more the data are spread out from the mean and the more variability one can expect in the observations.

Answer 3

- The percentages are generally much higher than what Chebyshev’s theorem specifies. These are reflected in what are called the empirical rules : 1. Approximately 68% of the observations will fall within one standard deviation of the mean, or between x - s and x + s . 2. Approximately 95% of the observations will fall within two standard deviations of the mean, or within x (plus or minus) 2 s . 3. Approximately 99.7% of the observations will fall within three standard deviations of the mean, or within x (plus or minus) 3 s.

Answer 4

also known as the z -score , provides a relative measure of the distance an observation is from the mean, which is independent of the units of measurement.

Answer 5

The coefficient of variation (CV) provides a relative measure of the dispersion in data relative to the mean. - The coefficient of variation provides a relative measure of risk to return. The smaller the coefficient of variation, the smaller the relative risk is for the return provided. The reciprocal of the coefficient of variation, called return to risk , is often used because it is easier to interpret. That is, if the objective is to maximize return, a higher return-to-risk ratio is often considered better.

Answer 6

- it describes the lack of symmetry of data. Those that tail off to the right, like this example, are called positively skewed ; those that tail off to the left are said to be negatively skewed. - The coefficient of skewness (CS) measures the degree of asymmetry of observations around the mean.

Answer 7

Statistics such as means and variances are not appropriate for categorical data. Instead, we are generally interested in the fraction of data that have a certain characteristic. The formal statistical measure is called the proportion , usually denoted by p. - they should be between 0 and 1.

Answer 8

the measure of the linear association between two variables X and Y

Answer 9

measure of the linear relationship between two variables X and Y which doesnt depend on the units of measurement. - its measured by the correlation coefficient

Answer 10

the likelihood that an outcome will occur

Answer 11

the collection of all possible outcomes of an experiment

Answer 12

1. the probability associated with any outcome must be between 0 and 1 2. the sum of the probabilities over all possible outcomes must be 1.0

Answer 13

a collection of one or more outcomes from a sample space 1. The probability of any event is the sum of the probabilities of the outcomes that comprise that event. 2. If A is any event, the complement of A , denoted A sample space not in Ac, consists of all outcomes in the sample space NOT in A. - The probability of the complement of any event A is P (Ac) = 1 - P(A) .

Answer 14

A numerical description of the outcome of an experiment. Formally, a random variable is a function that assigns a real number to each element of a sample space. - they can be discrete or continuous and they could be known or empirical

Answer 15

- A discrete random variable is one for which the number of possible outcomes can be counted. - A continuous random variable has outcomes over one or more continuous intervals of real numbers.