Mod. 1 Ch. 3 – Means and Standard Deviation – Flashcards

adding all values of variables and dividing by number of variables

mean computed by using all individuals in a population, symbol is "mew"

parameter

mean using sample data, symbol is "x-bar"

population

sample

population mean

sample mean

Uppercase sigma, and means the "sum of terms [xi]"

all x values

{sum of}{all x values}

sum of all x values / N - population

value that lies in the middle of the data when arranged in ascending order. M is the symble

find the middle value

take the mean of the middle 2 values

is the measure of central tendencies resitant to extreme values, does it alter the data significantly

median and mode

mean, range and standard deviation

variable that is most the most freequent observation, N or n's can be no mode, single mode, bimodal or multimodal

quantitative and qualitative

qualitative central tendency

difference between the largest data value and the smallest

because it doesn't give you how wide the data is talking about but not weather it's scrunched or dispersed or how many n or N is

(standard deviation)^2

to see how spread out or concentrated the data in a bell curve is, should be able to pic which graphs go with which µ and "x-bar" and σ

68%-95%-99.7% rule

68% >> (34% () 34%)

2 Standard deviations [95-68= 27/2 = 13.5] >> (13.5% | 34% () 34%|13.5%)

[99.7-95= 4.7/2 = 2.35% >> [2.35% |..|.. () ..|..|2.35%]

roughly all bell-shaped curves

What is the probability that a randomly selected time falls between 40 and 42 seconds?

the Kth percentile, denoted Pk of a set of data is a value such that K percent of the observations are less than or equal to the value represented by the percentile, like class rank but the percentil starts from low to high, so 5th percentile is 5% of population has this or less and so forth, 95th is the top 95% of the data, and 95% of individuals and this number or less

Q3 minus Q1

middle 50% of all observatoins

put data in order!!!! median will be skewed otherwise

0 because observations greater than the mean will offset the observations less than the mean and cancel out to zero or close to zero

The standard deviation is used in conjunction with the MEAN to numerically describe distributions that are bell shaped. The MEAN measures the center of the​ distribution, while the standard deviation measures the SPREAD of the distribution.

True, because the standard deviation describes how​ far, on​ average, each observation is from the typical value. A larger standard deviation means that observations are more distant from the typical​ value, and​ therefore, more dispersed.

the more spaced out and dispersed the bell shape.