lecture one

Question 1

Definition of biostatistics

Answer 1

The science of collecting, organizing, analyzing, interpreting and presenting data for the purpose of more effective decisions in clinical context.

Question 2

4 Importance of biostatistics

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Answer 2

1. Identify and develop treatments for disease and estimate their effects
2. Design, monitor, analyze, interpret, and report results of clinical studies
3. Identify risk factors for diseases
4. Develop statistical methodologies to address questions arising from medical/public health data

Question 3

When do you need biostatistics?

Answer 3

BEFORE you start your study!

Question 4

dx betw population and a sample

Answer 4

• Population includes all objects of interest
  
  • ​assoc w/ PARAMETERS(μ,σ)
• Sample is only a portion of the population
  
  • assoc w/ STATISTICS(X,s)

compute statistics, and use them to estimate
parameters.

Question 5

reasons why we dont work with populations

Answer 5

1. usually large, and often impossible to get
   data for every object of study
2. Sampling is costly, and the
   more items surveyed, the larger the cost

Question 6

Descriptive vs Inferential statistics

Answer 6

statistics are computed in order to estimate the parameters of a population

Descriptive Statistics

• first (computational) part of statistical analysis
• procedure used to organize and summarize masses
  of data

Inferential Statistics i

• second (estimated) part of statisticcal analysis
• used to find out info about a population, based on a sample

Question 7

define biased sample

Answer 7

Biased sample is one in which the method used to
create the sample results in samples that are
systematically different from the population.

Question 8

define random sampling

Answer 8

Each element/item in the population has an equal chance of
occuring.

• preferred way but difficult to execute
• requires complete list of each element in pop therefore usually assoc w/ comp gen list

Question 9

define systematic sampling

Answer 9

elements are counted off /every x-th element is taken

Question 10

OTHER TYPES OF SAMPLING

Answer 10

convenience sampling:

readily available data is used (first people the surveyor runs into.)

cluster sampling:

• divides the pop into groups/clusters usually geographically.
• clusters are randomly selected,
• each element in the chosen clusters are used.

Stratified sampling

• divides the population into groups called strata.
• by some characteristic,(M/F) not geographically
• sample taken from each strata using
  
  • random, systematic, or convenience sampling.

Question 11

3 things thtat determine a good sample

Answer 11

1. Random selection
2. Representativeness by structure
3. Representativeness by number of cases

Question 12

types of error

Answer 12

Random error = sampling variability.

Bias (systematic error) difference betw/ observed value and the true value due to all causes other than sampling variability.

absence of error of all kinds = accuracy

Question 13

sample size calculation principles

Answer 13

• law of large numbers= as the sample size increases the margin of error decreases as percentage diff betw/ popo and sample goes to zero
• number of experimental units are justified
• purpose of size calculation = large enough for acc info but small enough for practicality

Question 14

factors sample size depend on APEUS

Answer 14

Acceptable level of confidence

Power of the study

Expected effect size

Underlying event rate in the population

Standard deviation in the population

Question 15

stages of biomedical research

Answer 15

1. Planning and organization
2. Conduction of the investigation
3. Data processing and analyses of results

Question 16

8 components of research programme

Answer 16

1. Aim : summary and
   formulatation of the research hypothesis.
2. Object: event, that is going to be studied.
3. Units of observation: logical(studied case) and technical(evn of logical unit
4. Indices of observation: important mesaurable factors. they are *measurable*additive*self controlling
   
   1. factorial
   2. resultative
5. Place
6. Time:
   
   1. single: studied in single “critical’ moments
   2. continuous: show long term tendency of events
7. Statistical analyses
8. Methodology

Question 17

one vs many measurements

Answer 17

many measurements on one subject: get to know the one subject quite well but learn nothing about how the response varies across subjects.

one measurement on many subjects, you learn less about each individual, but you get a good sense of how the response varies across subjects.

Question 18

explain paired and unpaired data

Answer 18

paired: 2+ measurements are made on the same observational unit (subjects, couples)

unpaired: only one type of measurement is made on each unit.

Question 19

describe the parts of the research plan in planning and organisation

Answer 19

• Definition of the team responsible for the study and preliminary training.
• Administration and management of the study.

Question 20

key components of information processing

Answer 20

• Data check and correction
• Data coding
• Data aggregation
  
  • according to data use: Primary /Secondary
  • according to indice number: Simple /Complex

Question 21

benefits of data summary

Answer 21

• become familiar with the data and the characteristics of the sample that you are studying
• identify problems with data collection or
  errors in the data (data management issues)
• Range checks for illogical values

Question 22

dx betw/ variable and data

Answer 22

variable: ​something whose value can vary.
data: values obtained from measuring a variable

Question 23

categories of variables

Answer 23

Nominal

• Values in arbitrary categories
• Order of the categories is completely arbitrary/ meaningless
• No units!
• Data has no units of measurement.

Ordinal

• Values in ordered categories
• Order of the categories is not arbitrary. possible to
  order the categories in a meaningful way.
• No units!
• Data do not have any units of measurement.

Question 24

what are the four levels of measurement

Answer 24

• Nominal is the lowest level. Only names are meaningful here.
  
  • genotype- no numbers calc is meaningless
• Ordinal adds an order to the names.
  
  • pain score-order matters but not diff betw
• Interval adds meaningful differences.
  
  • temp- diff betw 2 points
• Ratio adds a zero so that ratios are meaningful.
  
  • height- clear def of 0, can look at the ratio of 2 measurements

Question 25

visual methods to summarize data

Answer 25

• tables
  
  • frequency table
• graphs/ graphical summary
  
  • bar chart = categorical data
  • histogram = continuous data
  • boxplot= continous data