Lecture 2

Question 1

what are statistically methods useful for

Answer 1

studying, analyzing, and learning about populations of experimental units

Question 2

define experimental or observational unit

Answer 2

an object about which we collect data
person, thing, event, tree
thing we measure

Question 3

define population

Answer 3

set of all units - all possible measurements we could take
set of all unit that we want top study
can be infinite

Question 4

define variable

Answer 4

what we observe
characteristic or property of an individual experimental or observational unit in population
like age, weight, counts

Question 5

define experiment

Answer 5

measure outcome of some physical action we take

Question 6

define sample

Answer 6

a subset of units in population
Collection of observations we make
represents pop

Question 7

describe random sample

Answer 7

assume some things about how data was collected

Question 8

define statistical inference

Answer 8

estimate, prediction or some generalization about population based on info contained in sample
does evidence in data support physical law
Characteristic

Question 9

describe sample mean

Answer 9

sample mean = sum of observations/# of obs

Question 10

describe measure of reliability

Answer 10

statement
usually quantitive
about a degree of uncertainty associated with a statistical inference = using limited number of obs= wont learn everything
based on data of sample

Question 11

give examples of measure of reliability

Answer 11

flipping coin = heads all 3 times= chance of heads is 1
but experiment limited
based on data of sample = size mainly

Question 12

how many things do we need to determine in study

Answer 12

7 things

Question 13

name all 7 things we need to determine in study

Answer 13

1 - Objectives of study
2 - experimental units
3 - population under study
4 - characteristic(s) of interest
5 - sample
6 - inference(s) of interest
7 - measure(s) of reliability

Question 14

describe objectives of study - determine in study

Answer 14

what questions we want to answer in study
important for ethics approval if using humans

Question 15

describe experimental units - determine in study

Answer 15

people
machines
transactions
what we could possibly measure

Question 16

describe population under study - determine in study

Answer 16

set of experimental units
(all first year undergrads, all transactions at Walmart in a day)

Question 17

describe characteristic of interest - determine in study

Answer 17

variable(s) measured on th experimental unit
can measure multiple but mainly we focus on one

Question 18

describe sample - determine in study

Answer 18

subset of pop under study
if we could = take census (whole population) but if cannot= take sample

Question 19

describe inferences of interest- determine in study

Answer 19

about pop based on sample

Question 19

describe measure of reliability- determine in study

Answer 19

to account for limited sample

Question 20

describe infinite vs finite pop

Answer 20

if finite = sample = all the obs units = population = census
but infinite = # of possible experimental units we could get is infinitely large

Question 21

describe sub cutaneous fat necrosis in newborns - generally

Answer 21

Some newborns suffer asphyxia during birth
A treatment for perinatal asphyxia is called therapeutic hypothermia= involves lowering the child’s body temperature for 72 hours, then the child’s body temperature is slowly raised to normal
Some children develop the rare condition sub-Cutaneous fat necrosis (SCFN)= this usually disappears within a few weeks but some children develop more serious complications

Question 22

describe sub cutaneous fat necrosis in newborns - population

Answer 22

all full term newborns who may suffer from perinatal asphyxia that will get hypothermia as treatment (units of interest)

Question 23

describe sub cutaneous fat necrosis in newborns - variable of interest

Answer 23

if child developed scfn (yes/no)
birthweight (sample mean)
other risk factors
could measure all or specific one

Question 24

describe sub cutaneous fat necrosis in newborns - sample

Answer 24

term asphyxiated newborns admitted to montreal childrens hospital NICU from aug 2008 –> march 2015

Question 25

describe sub cutaneous fat necrosis in newborns - inference

Answer 25

one estimation of birthweight for those who developed scfn
report sample mean and try to extrapolate and reflect pop

Question 26

describe inference more detailed

Answer 26

drawing conclusions from data about pop
also use word to pose question and answer it

Question 27

describe quantitative data

Answer 27

Measurements recorded on naturally occurring numerical scale
Numerical measurement
ordinal
ex = height, blood pressure, temperature, counts

Question 28

describe qualitative data

Answer 28

Measurements cannot be made in a natural numerical scale
can only ascertained and classified into one of several groups or categories
nominal
no natural order
ex= gender, presence of disease, religion, ethnicity, coin toss, faculties, colours

Question 29

describe the methods of obtaining data

Answer 29

published sources = literature, books, government, publications
designed experiments
observational studies

Question 30

describe designed experiments

Answer 30

researcher designs experiment = has control over experimental units sampled = can intervene and change what is going on
usually 2 groups = group of experimental units assigned to a treatment and another untreated
may involve more than 2 groups
like clinical trial, best for science
can have heterogeneity = can control so much, less variability

Question 31

give ex of fertilizer study for designed experiments

Answer 31

claim = organic fertilizer increases yield and size of tomatoes compared to other brand
Experiment = tomato plants assigned to 2 groups = organic and reg fertilizer
size and weight of each tomato recorded and total yield
RESEARCHER has control over what plant gets which fertilizer

Question 32

describe observational studies

Answer 32

Sometimes unethical or impossible to assign treatment to a group (money, cannot deny standard of care)
researcher can only observe - indirectly or directly the experimental units and record variables of interest
cheaper but can be hidden sources of variability bc don’t have control over what groups are doing specifically

Question 33

ex of obs study = smoking and lung cancer

Answer 33

cannot assign smoking and non smoking groups = cannot be randomized bc unethical, also we know relationship now = health hazard
possible approach = select cancer and non cancer patients and determine whether they were smokers or not from records
RESEARCHER can only observe directly or indirectly the experimental units and records variables of interest = smoking status

Question 34

describe iron man competition

Answer 34

swim, bike, marathon, no break
some athletes develop hyponatremia during race = abnormally low levels of sodium in blood
can lead to health issues and death
mild case can be treated with iv saline solution

Question 35

describe what investigators interested in for iron man comp

Answer 35

determining possible causes of hyponatremia
testing whether oral saline solution as effective as iv saline for treating mild case

Question 36

explain objective 1 of iron man comp

Answer 36

causes of hyponatremia

cannot indue or provoke in subjects
can only wait for it to occur in some althltes during race
then can make comparisons between who got it and who didn’t
OBSERVATIONAL STUDY

Question 37

explain objective 2 of iron man comp

Answer 37

testing treatments
consider only those who suffered hyponatremia during race
make 2 groups by assigning at random some to oral and some get iv
have control over who gets what
Compare effectiveness of treatments between groups
DESIGNED EXPERIMENT

Question 38

why would a researcher restrict population

Answer 38

for homogeneity of pop and effect we look at
like for age = common restriction