Lec1 - The first steps in understanding data Describing it!...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
The first steps in understanding data … I. Frequency distributions II. Measures of center III. Measures of dispersion Describing it! Descriptive statistics tell us about the shape, center and spread of the data Inferential statistics allows us to draw general scientific conclusions from our data
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Grouped frequency distributions Creatine phosphokinase mode Right tail Left tail Skewed to the right
Background image of page 2
Areas in histograms 100% 15/36 = 42% 7/36 = 19% 16/36 = 44%
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Shapes of frequency distributions Approximation of a histogram by a smooth curve symmetric skewed to the right skewed to the left bell shaped not bell shaped bimodal
Background image of page 4
The first steps in understanding data … I. Frequency distributions II. Measures of center III. Measures of dispersion Describing it! Descriptive statistics tell us about the shape, center and spread of the data Inferential statistics allows us to draw general scientific conclusions from our data
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Descriptive statistics II: Measures of Center Mean: sum of the observations divided by number of observations Y is a variable y is the mean y = y i i = 1 n n = y 1 + y 2 + + y n n length weight rainfall concentration offspring Y is the length of a radish shoot y 1 , y 2 , y 3 , … y n are observations in a sample y 1 y 2 y 3 y 4 y 5 y 6 y 7 = 15 = 20 = 22 = 20 = 29 = 37 = 11 y 8 y 9 y 10 y 11 y 12 y 13 y 14 = 35 = 15 = 30 = 8 = 25 = 33 = 10 y = 15 + 20 + 22 + 20 + 29 + 37 + 11 + 35 + 15 + 30 + 8 + 25 + 33 + 10 14 = 22.14 mm
Background image of page 6
Deviation: difference between a data point and the mean deviation i = y i y Deviation 1 = y 1 -y = 15-22.14 = -7.14 Deviation 2 = y 2 -y = 20-22.14 = -2.14 Deviation 3 = y 3 -y = 22-22.14 = -0.14 Deviation 4 = y 4 -y = 20-22.14 = -2.14 Deviation 5 = y 5 -y = 29-22.14 = 6.86 Deviation 6 = y 6 -y = 37-22.14 = 14.86 ( y i y ) i = 1 n = 0 Sum of deviations: The mean is the center of the distribution 10 20 30 22.14 y 1 y 2 y 3 y 4 y 5 y 6 y 7 = 15 = 20 = 22 = 20 = 29 = 37 = 11 y 8 y 9 y 10 y 11 y 12 y 13 y 14 = 35 = 15 = 30 = 8 = 25 = 33 = 10
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The median Median: the middle value of the sample To calculate the median: 1. Order the observations in increasing order
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 30

Lec1 - The first steps in understanding data Describing it!...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online