resecon212

If the distribution of the data is normal Chebyshev?s Theorem states that at least 75% of the data will lie with (i) standard deviations of the mean, and the empirical rule state that 68.26% of the data will lie within (ii) standard deviations from the mean.

(i) = 2, (ii) = 1

We use (i) to draw inference or make conclusions about (ii).

(i) sample statistics (ii) population parameters

If data is normal, Chebyshev's theorem states that at least 88.89% of the data will lie within (i) standard deviations of the mean and the empirical rule states that 95% of the data will lie within (ii) standard deviations from the mean

(i)3, (ii)2

Consider two events, A and B, P(A)=0.7, P(B)=0.4, and P(A or B)=0.6, the P(A and B)= ???

0.5

Consider data on a random variable with a maximum value of 100, a minimum value of 16. You wish to construct a histogram to summarize the data, and you have chosen to use 8 bins. What is the exact bin width?

10.5

Consider the following data consisting of 19 observations. What is 1st quartile? 10,13,14,15,15,16,18,25,25,26,26,26,27,29,30,32,35,35,38

15

a random variable has mean of 10 and standard deviation of 3. what is value of the random variable which corresponds to a z-score of 2?

16 (multiply z score by standard deviation and add the variable)

If a sample of 120 observations fall into 8 categories, the frequency of the first 4 and last categories are: cat 1: 6 cat 2: 16 cat 3: 8 cat 4: 25 ...cat 8: 32 what is cumulative frequency of category 3 in percentages?

25%

Consider the following data consisting of 19 observations. What is 2nd quartile? 10,13,14,15,15,16,18,25,25,26,26,26,27,29,30,32,35,35,38

26

Consider the following data consisting of 19 observations. What is 3rd quartile? 10,13,14,15,15,16,18,25,25,26,26,26,27,29,30,32,35,35,38

30

if you have a sample of n=150 observations of a continuous random variable and you wish to construct a histogram to summarize the distribution of the data, after using Sturges rule to compute the optimal number of bins you find bin width to be exactly 8.5, what is the range of data?

76.5

consider the 15 observations, what is the interquartile range 10, 12, 14, 15, 15, 16, 17, 19, 19, 19, 19, 23, 24, 24, 24

8 (Q3-Q1) --> (12-4)

currently there are 600 students in class. I ask 7 questions. if everyone responds, what does out data consist of? (variables and observation amount)

8 variables, 600 observations

Suppose you have a sample of n = 150 observations of a continuous random variable, and you wish to construct a histograms to summarize the distribution of the data. Using Sturges Rule, what is the appropriate number of bins?

9

What is Sturges rule?

Sturge's Rule: k = 1 + 3.322(log(n)) k is the number of classes n is the size of the data.

Consider 3 random variables, X, Y, and Z. If the correlation coefficient between X and Y is 0, and the correlation coefficient between Z and Y is -0.98, then which of the following can be said about their relationships/how they are related?

X and Y are linearly unrelated, and Z and Y are strongly, inversely, and linearly related

define covariance

a measure of linear association between two variables

how do you find cumulative frequency?

add up all the frequencies and divide by number of them...this gives you percentage

What does inferential statistics do?

allows you to make predictions ("inferences") from that data, you take data from samples and make generalizations about a population

nominal

categorical, values indicate quality, no order, hair color, eye color, where in US do you live

ordinal

categorical, values indicate ranking/order, how do you feel (happy-unhappy) (satisfied-unsatisfied)

if you use a simple form of probability that has equal odds of something happening what approach to assigning probabilities did you apply?

classical

if you gather info made up of people who are easy to reach what approach to assigning probabilities did you apply?

convenient

What does descriptive statistics do?

describes data (for example, a chart or graph)

if you use your observation through experiments what approach to assigning probabilities did you apply?

empirical

how do you find covariance?

multiply (x-xavg)(y-yavg) then add up all those and divide by the amount of numbers-1 (n-1)

on a line graph, is two random variables are reflected horizontally, how are they correlated (neg, pos, under, un)

negatively correlated

if distributions of data is norma, is the percentage of the data in empirical rule that lies within k standard deviations from mean always less than minimum percentage of data in chebyshev?

no

interval

numeric, interval has meaning, temperature, between dec 1999-feb 2000

ratio

numeric, interval, there is a true zero, number of books on shelf, weight of heaviest book

Consider the following survey question. How satisfied are you with the pizza selection on campus? 1) Very Unsatisfied 2) Unsatisfied 3) Neutral 4) Satisfied 5) Very Satisfied What level of measurement is the response?

ordinal

If ages in resecon range from 19-24, consider the question: how old are you (in years)? 1. 19 2. 20 3. 21 4. 22 5. 23 6. 24 what level of measurement is the response?

ratio

a farmer has 20 acres of land on which he grows corn and wishes to conduct a random sample to evaluate the quality of the corn, he knows the soil is 10 acres to the right of the center is poor relative to the other 10 acres to the left, he decides to randomly select more corn from the region right of the center than the left. this method of sampling:

stratified sampling

If you use your opinion/judgement about how likely something is to occur, what approach to assigning probabilities did you apply?

subjective

What is the key visual difference between a histogram and bar chart?

the bars in the histogram should touch

If a graph curve is thinner and taller, what is the difference in mean/variance compared to a curve that is wider and flatter?

the thinner and taller curve has a larger mean and larger variance