Week 3: Measurement, reliability and validity Flashcards
Explain each term regarding exposure measurement:
1. Available dose (cumulative vs current)
2. Administered dose
3. Absorbed dose/uptake
4. Active dose
- cumulative active dose = total amount given to a patient over time
current active dose = amount given to a patient at a specific time - administered dose = amount that comes in contact; can be administered in different routes
- absorbed dose/uptake = amount that actually enters the body
- active dose = how much actually had a biological effect on the target site
45 individuals older than 75 admitted to the hospital in Toronto for a shoulder dislocation in the past year. This is an example using the term _________
count
- What is ratio? Give an example
- What is proportion? Give an example
- ratio = relationship to COMPARE 2 numbers. The numerator is NOT necessarily included in the denominator. Ex: binary sex ratio –> 5/2 = 5:2 ratio of boys compared to girls
- proportion = relationship to show something OUT OF the total number. The numerator MUST be included in the denominator. Ex: binary sex proportion –> 2/4 are girls = 50% girls
- What is odd?
- In a population of 100 people, 25 people are diabetic. What is:
a) the proportion of diabetes
b) the odd of being a diabetic
- the probability of an event occurring relative to it not occurring
- a) proportion = 25/100 = 0.25
b) odd = 25/75 = 0.33 –> probability of event occurring (25 people have it) over it not occurring (75 people do not have it)
- What is rate? Explain the numerator and denominator in a rate expression
- Write a rate for this situation: In 2021, 25 people were diagnosed with chronic bronchitis. The population at risk consisted of 1000 people.
- Rate = speed of occurrence of an event over time
numerator = # of events observed for a given time
denominator = population that is at risk in which the events occur –> incorporates a period of time - 25/1000 = 0.025 of pop/year (2021) had chronic bronchitis
- What is prevalence rate?
- What are the 2 types? Explain (use formula)
- prevalence rate = proportion of the population that HAS a given disease at a specific TIME
- Point PR = # with disease at a specific time/ total # of people in pop at same time
Period PR = # with disease during time period/ total # of people in pop at same time
If 3 million people in Canada have diabetes NOW and the current Canadian population is 30 million, what is the point PR of diabetes per 1000 people?
= 3 million / 30 million = 0.1 = 10% / 1 person
per 1000 = 0.1 x 1000 = 100 cases / 1000 people
In 2018, Montreal had a population of 152358. There were 6 cases of mononucleosis. What is the period PR of mononucleosis during 2018 per 100,000 persons?
Period PR = 6/152358 = 0.00004 per person x 100,000 = 4 per 100,000 persons
- What is incidence rate? Give the formula
- What type of studies are incidence rates obtained from:
a) randomized controlled trials
b) cohort (longitudinal) studies
c) case-control studies
d) clinical trials
- The proportion of the population AT RISK that develops a given disease or other attribute during a specified time period.
IR = # of new cases during a specified time period/ population “at risk” - b)
describe the relationship between prevalence and incidence and what results
incidence (those at risk) —> can become prevalence (those with the disease) —> which leads to the resolution (recovery or death)
9,000 residents of Toronto were studied on Jan 1, 2010. Of these residents, 245 had a history of cancer. By Dec 31, 2019 a total of 179 new cases of cancer had been diagnosed in the “at risk” population. What is the 10-year cumulative incidence rate of cancer (first diagnosis) in this cohort per 10,000 people?
IR = 179 / (9000-245) = 0.02 x 10,000 = 204 per 10,000 people.
*the at risk population (denominator) is the total pop - those who have already had cancer since we need to find a first diagnosis IR.
2,012 first year university students were sampled in Sept 2021. Of these, 112 had depression. In May 2022, 345 of the sample had depression, including 79 of those who had depression in September.
a) What was the prevalence of depression Sept 2021 and May 2022?
b) How many “resolution” cases were there?
c) What is the IR of new depression cases during the freshman year (Sept 2021 to May 2022) ***don’t understand answer
d) why do we remove those with depression diagnosed at the beginning of the study from the population at risk in part c)?
a) Sept 2021 IR= 112/2012 = 0.056 = 5.6%
May 2022 IR= 345/2012 = 0.17 = 17%
b) 112 - 79 =33
c) IR= (345-79)/ (2012-112) = 266/1900 = 0.14 = 14%
d) because these people have already had depression so they can not be at risk of developing a NEW case of depression. So they are excluded from the population at risk (denominator)
Incidence measures frequency of disease _______. Prevalence measures population disease _______
onset
status
- What is relative risk?
- relative risk tells us the _______ of an association
- What does relative risk NOT tell us?
- How is it calculated?
- tells us how many times as likely it is that someone who is “exposed” to something will experience a specific outcome compared to someone not exposed
- Strength
- does NOT tell us anything about how much MORE disease is occurring
- Make the table, will be incidence in exposed/incidence in unexposed
RR= [a/(a+b)] / [c/(c+d)]
The results of a study evaluating the effects of calling patients and their likelihood to receive a influenza immunization revealed:
- those who received a call and got immunized = 328
- those who received no call and got immunized = 288
- those who received a call and did not get immunized = 332
- those who did received no call and did not get immunized = 370
What is the RR of those who received a call compared to those who did not. What do the results indicate?
exposure = receiving a call
outcome = getting immunized
RR= [328 / (328+332)]/[288 / (288+370)] = (328/660) / (288/658) = 0.49/0.43 = 1.14 or 14% more likely to attend for immunization