stats 212 wsu exam 1 fully solved and updated

Qualitative variable - answer-take on values that are names or labels. The color of a ball (e.g., red, green, blue) or the breed of a dog (e.g., collie, shepherd, terrier) would be examples of categorical variables. Quantitative variable - answer-They represent a measurable quantity. For example, when we speak of the population of a city, we are talking about the number of people in the city - a measurable attribute of the city. Therefore, population would be a quantitative variable. Discrete - answer-Discrete variables are countable in a finite amount of time. For example, you can count the change in your pocket. You can count the money in your bank account. You could also count the amount of money in everyone's bank account. continuous - answer-Continuous Variables would (literally) take forever to count. In fact, you would get to "forever" and never finish counting them. For example, take age. You can't count "age". Why not? Because it would literally take forever. For example, you could be: 25 years, 10 months, 2 days, 5 hours, 4 seconds, 4 milliseconds, 8 nanoseconds, 99 picosends...and so on. You could turn age into a discrete variable and then you could count it. For example: A person's age in years. A baby's age in months. Parameter - answer-numerical summary of a population Statistic - answer-a number that describes a sample What is an experiment - answer-In an experiment investigators apply treatments to experimental units (people, animals, plots of land, etc.) and then proceed to observe the effect of the treatments on the experimental units. What is an observational study - answer-a study where researchers simply collect data based on what is seen and heard and infer based on the data collected. Researchers should not interfere with the subjects or variables in any way. True or false: Standard deviation is equal to the variance squared - answer-False True or false: If a and b are independent then A and B can never be mutually exclusive (Assume PA and PB are non-zero) - answer-true T or F: The median is a measure of central tendency that is resistent to extreme values - answer-True T or F: The empirical rule can be applied to all data sets (both bell-shaped and non-bell-shaped) - answer-F Simple random sample - answer-The size consists of N individuals from the population chosen in usch a way that every set of individuals has an equal chance of being selected. (ex:100 names are drawn at random from a box containing all of the entries for a raffle. ) Systematic random sample - answer-(ex: A random name is drawn from the first 50 names on a list and then each 50th name thereafter is selected) Stratified random sample - answer-First divide the population of indivduals into groups and then taking a random sample of each group. (ex:In every franchise of a restaurant, a random sample of customers is selected to provide their opinions on customer service. ) Clustered random sample - answer-With cluster sampling, the researcher divides the population into separate groups, called clusters. Then, a simple random sample of clusters is selected from the population. The researcher conducts his analysis on data from the sampled clusters. (ex:A random sample of 5 regional offices are selected and every transaction is audited for accuracy ) Mode - answer-To find the mode, or modal value, it is best to put the numbers in order. Then count how many of each number. A number that appears most often is the mode. can be used for both numerical and categorical variables Median - answer-To find the Median, place the numbers you are given in value order and find the middle number. resistent to outliers. Mutually exclusive - answer-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. What does the r^2 value represent - answer-R-squared is a statistical measure of how close the data are to the fitted regression line. It is also known as the coefficient of determination, or the coefficient of multiple determination for multiple regression. 0% indicates that the model explains none of the variability of the response data around its mean. individuals vs. populations - answer-your sample is the group of individuals who actually participate in your study. These are the individuals who you end up interviewing (e.g., in a qualitative study) or who actually complete your survey (e.g., in a quantitative study). On the other hand, your population is the broader group of people to whom you intend to generalize the results of your study. Your sample will always be a subset of your population. Your exact population will depend on the scope of your study. How do you calculate standard deviation? - answer- calculating the probability of A and B - answer-multiply the probability of A and the probability of B together calculating the probability of A or B - answer-P(A or B) = P(A) + P(B) - P(A and B) Calculating conditional probability - answer-The conditional probability of an event B is the probability that the event will occur given the knowledge that an event A has already occurred. This probability is written P(B|A), notation for the probability of B given A. What makes two events independent? - answer-When two events are said to be independent of each other, what this means is that the probability that one event occurs in no way affects the probability of the other event occurring. Prospective vs. Retrospective - answer-A prospective study watches for outcomes, such as the development of a disease, during the study period and relates this to other factors such as suspected risk or protection factor(s). The study usually involves taking a cohort of subjects and watching them over a long period. A retrospective study looks backwards and examines exposures to suspected risk or protection factors in relation to an outcome that is established at the start of the study. Many valuable case-control studies, such as Lane and Claypon's 1926 investigation of risk factors for breast cancer, were retrospective investigations. sampling bias - answer-introduced when the way the sample is selected systematically excludes some part of the population. response bias - answer-Response bias (also called survey bias) is the tendency of a person to answer questions on a survey untruthfully or misleadingly. For example, they may feel pressure to give answers that are socially acceptable nonresponse bias - answer-when responses are not actually obtained from all participants how to calculate range? - answer-subtract the largest measurement minus the smallest measurement. Pearson correlation coefficeint - answer-(r) means the strength and the direction of a straight line relationship What is a residual plot? - answer-The difference between the observed Y and the predicted Y What are the percentages in a bell shaped graph? - answer-34%, 13.5%, 2.35%, .15%