Lecture 2 Flashcards

1
Q

what are statistically methods useful for

A

studying, analyzing, and learning about populations of experimental units

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2
Q

define experimental or observational unit

A

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

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3
Q

define population

A

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

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4
Q

define variable

A

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

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5
Q

define experiment

A

measure outcome of some physical action we take

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6
Q

define sample

A

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

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7
Q

describe random sample

A

assume some things about how data was collected

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8
Q

define statistical inference

A

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

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9
Q

describe sample mean

A

sample mean = sum of observations/# of obs

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10
Q

describe measure of reliability

A

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

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11
Q

give examples of measure of reliability

A

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

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12
Q

how many things do we need to determine in study

A

7 things

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13
Q

name all 7 things we need to determine in study

A

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

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14
Q

describe objectives of study - determine in study

A

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

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15
Q

describe experimental units - determine in study

A

people
machines
transactions
what we could possibly measure

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16
Q

describe population under study - determine in study

A

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

17
Q

describe characteristic of interest - determine in study

A

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

18
Q

describe sample - determine in study

A

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

19
Q

describe inferences of interest- determine in study

A

about pop based on sample

19
Q

describe measure of reliability- determine in study

A

to account for limited sample

20
Q

describe infinite vs finite pop

A

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

21
Q

describe sub cutaneous fat necrosis in newborns - generally

A

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

22
Q

describe sub cutaneous fat necrosis in newborns - population

A

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

23
Q

describe sub cutaneous fat necrosis in newborns - variable of interest

A

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

24
describe sub cutaneous fat necrosis in newborns - sample
term asphyxiated newborns admitted to montreal childrens hospital NICU from aug 2008 --> march 2015
25
describe sub cutaneous fat necrosis in newborns - inference
one estimation of birthweight for those who developed scfn report sample mean and try to extrapolate and reflect pop
26
describe inference more detailed
drawing conclusions from data about pop also use word to pose question and answer it
27
describe quantitative data
Measurements recorded on naturally occurring numerical scale Numerical measurement ordinal ex = height, blood pressure, temperature, counts
28
describe qualitative data
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
29
describe the methods of obtaining data
published sources = literature, books, government, publications designed experiments observational studies
30
describe designed experiments
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
31
give ex of fertilizer study for designed experiments
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
32
describe observational studies
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
33
ex of obs study = smoking and lung cancer
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
34
describe iron man competition
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
35
describe what investigators interested in for iron man comp
determining possible causes of hyponatremia testing whether oral saline solution as effective as iv saline for treating mild case
36
explain objective 1 of iron man comp
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
37
explain objective 2 of iron man comp
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
38
why would a researcher restrict population
for homogeneity of pop and effect we look at like for age = common restriction