Scatterplots

Question 1

what 2 data types do they provide? (think back to week 2!)

Answer 1

relationship data

distribution data

Question 2

two alternate names for the X variable

Answer 2

explanatory variable

covariate

Question 3

alternate name for Y variable

Answer 3

response variable

Question 4

in scatterplots, X variable may be what type of variable

Answer 4

categorical or continuous

Question 5

in scatterplots, Y variable must be

Answer 5

continuous

Question 6

2 directions of X-Y relationship

Answer 6

positive (X increases, Y increases)

negative (X increases, Y decreases)

Question 7

3 shapes of X-Y relationship

Answer 7

linear
non linear
clusters

Question 8

main statistic that scatterplots look at

Answer 8

correlation coefficient, r

Question 9

values that r can take?

what two factors does it quantify?

Answer 9

-1 to +1

strength ( | number | ) and direction (+/-) of relationship

Question 10

fairly weak correlation?

Answer 10

0 - 0.3 |

Question 11

fairly strong correlation?

Answer 11

0.3 - 0.7 |

Question 12

strong correlation?

Answer 12

0.7 - 0.9 |

Question 13

very strong correlation?

Answer 13

0.9 - 1 |

Question 14

R^2 value shows us

Answer 14

what proportion of variation in Y can be explained by variation in X?

Question 15

correlation is not

Answer 15

causation

Question 16

key assumption when making scatterplot?

Answer 16

data points are independent

Question 17

null and alt hyp?

Answer 17

null: r = 0 (no relationship)
alt: r =/= 0

Question 18

what can we calculate by hand?

Answer 18

t score, degrees of freedom (number of pairs - 2), 2 tailed p value