Stat 371 1nd Edition Exam 1 Study Guide Lectures 1 12 Lecture 1 Wed 9 3 Why do we have to take this class Stats are in all medical articles Stats prove disprove all hypotheses What stats does Stats takes a random sample from a population in order to make an inference about a particular problem Population all subjects of interest Sample subset of population some of subjects of interest Inference info from sample to draw conclusions about a population Random sample where every member of the population has the same chance of being chosen independently of each other Lecture 2 Fri 9 5 Statistics numerical measurement derived from sample data numerical letters s s 2 x 2 Parameter numerical measure derived from the population greek leters 2 o We use statistics to infer something about parameter Descriptive statistics describe a set of data sample Variable characteristic of a subject that can be assigned or category o Categorical in categories Ordinal order rank matters Nominal order doesn t matter o Numeric numbers Continuous can take the form of any real number on number line Discrete only can take specific values 1 2 3 4 Observational Unit item on which a variable measure is taken what is the thing that you measure variable on Frequency Distribution a graphical representation of the number of times a particular unit occurs similar to a bar chart aka histogram o Shows us where the middle is where most of the data lies spread of the data How to make a frequency distribution o X axis Bins either the categories of the data intervals of s that the data take o Y axis Frequency of times a from that bin occurs OR Relative Frequency of times a from that bin occurs Frequency n Shapes of frequency distribution 6 o Unimodal has one mode Mode a central peak bin where the greatest of data occurs o Symmetric same on both sides o Biomodal has two modes o Exponential an extremely right skewed distribution left most pt is the highest and it decreases as it moves right o Right skewed there is a longer right tail mean is higher than the median o Left skewed there is a longer left tail mean is lower than the median Lecture 3 Mon 9 8 Median the value that lies in the center of the data split data into 2 equal parts Mean average denoted by x and o X bar is a statistic sample is a parameter population Quartiles median not included in q1 and q2 o Q1 median of the lower half of data set o Q2 median of entire data set o Q3 median of the upper half of data set Interquartile range IQR the difference between Q3 and Q1 50 of data Boxplot visual representation of a data set using the Q1 Q2 and Q3 min and max Modified boxplots account for outliers data pts that don t fit w the other data pts o Lower fence left whisker whichever is bigger min of data or Q1 1 5 IQR o Upper fence Right whisker whichever is smaller max of data or Q3 1 5 IQR o If a number in data set falls outside of fences the it is denoted by an Lecture 4 Wed 9 10 Range the difference between the max and min numbers in a data set Deviation the difference between a data point and the mean squared o xi x 2 variance average of the squared deviations denoted as s2 statistic or 2 parameter o xi x 2 n 1 Standard deviation s2 a unit of measurement in statistics denoted by s or Empirical rule about 68 of observations fall within 1 SD of the x s o About 95 of observations fall within 2 SD of the x 2s o About 99 of observations fall within 3 SD of the x 3s Coefficient of variation the standard deviation expressed as a percentage of the mean o s x 100 Interpretation the standard deviation is as large as the mean Lecture 5 Probability Fri 9 12 Probability a numerical quantity that expresses the likelihood of an event Experiment a process or study which results in the collection of data Outcome a possible result of an experiment Event any set of outcomes in an experiment Sample Space the set of all possible outcomes in an experiment To find Probability o outcomes in the event outcomes in the sample space o Notation P A Complement probability of an event NOT occurring o Notation A o P A 1 P A Either A or B happens A U B A and B happens A B Mutually Exclusive two events have no interaction probability of A intersect B 0 Conditional Probability probability can change when we condition it on another event occurring Notation P A B o given o The probability of event A happening given event B has occurred Identifying mathematical expressions in word problems o Label events with letters that represent them o Try to figure out what type of probability it is union intersection conditional o And interactions o IF and GIVEN typically represent conditional probabilities o OR represents union For events to be independent the outcome of one event doesn t affect the outcome of the other events o 2 events are considered independent of one another
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