Stat Chapter 1 Flashcards
(14 cards)
Population
It is a well defined collection of objects.
Census
When all the desired information is collected about the objects.
Sample
A subset of the population
Variable
Any characteristic that may change from one object to another.
Two branches of Statistics
Descriptive statistic is like the way we collect present summarize and and describe important aspects of the data.
Inferential statistics is when we use sample of data to draw a conclusion about the population.
Stem and leaf display
a graphical representation for presenting quantitative data.
it tells mostly of location, spread, extremes and gaps
Dot plot
A summary of numerical data when the data set is reasonably small or few distinctive data values.
Discrete and continuous variable
it is discrete if its set of possible values are finite or infinite in sequence.
IT is continuous if it has some interval on the number line
Relative Frequency
the fraction of times the value occurs.
About number of ‘‘classes’’
number of classes = sqrt of number of observations.
Unimodal histogram
Usually rises to a single peak and then declines.
Skewness, when is it positive or negative.
It is positively skewed if the right or upper tail is stretched out.
Negatively skewed if it is stretched to the left .
Kutosis, when negative and positive
It is more of a description of the shape of a probability distribution. Like if it is heavy or light tailed to a normal distribution.
A negative one indicates a flatter peak and lighter tails
A positive one indicates a heavier tail.
Trimmed mean
It is a compromise between the mean and median. It is done by taking out the highest and smallest 10 % of observations to eliminate outliers which will give more a representative answer.
