118 Questions
Which term is used to describe a numerical characteristic of a population?
Parameter
What does the sample mean 'x-bar' represent?
Sample statistic
What is the relationship between parameters and statistics?
Statistics are estimates of parameters
How do 'observed' values help towards a knowledge of the 'true' values?
By allowing us to test hypotheses about the observed values
What type of value does sample mean 'x-bar' estimate?
Population parameter
What is the odds ratio used for in epidemiological studies?
Comparing patients with a certain condition to patients without that condition
In a 2x2 contingency table for a case-control study, what does 'a' represent?
Cases with the risk factor and the primary outcome
What does the odds ratio estimate in a case-control study?
Population relative risk
What do epidemiologists hope to achieve when estimating population characteristics like incidence and prevalence?
To obtain precise measurements of the true values
What does hypothesis testing allow statisticians to do?
Formally accept or reject statistical hypotheses
What is the purpose of interpretation in hypothesis testing?
To assess the strength of evidence against a hypothesis
What is the probability known as in hypothesis testing?
p-value
In epidemiological studies, what does random variation refer to?
The distortion of results by chance in observed data
What kind of statement can be made informally about observed data?
"The true values are probably fairly close to what we observed"
What is the argument structure used in interpretation of observed incidence rate ratios (IRR)?
'True' IRR vs. observed IRR vs. probability of observing IRR by chance
What does hypothesis testing allow statisticians to do?
Formally accept or reject statistical hypotheses
What is the purpose of interpretation in hypothesis testing?
To assess the strength of evidence against a hypothesis
What is the difference between systematic and random variation?
Systematic variation is a consistent difference between the recorded value and the true value, while random variation is due to chance differences in true and recorded values.
Which of the following best describes random variation?
Random variation involves chance differences in the true and recorded values.
Why might the incidence of TB fluctuate up and down on different occasions?
Because of the influence of random variation.
What is the 'true' risk referred to in the context of epidemiological observations?
The underlying risk or incidence that may be affected by random variation.
How is the proportion of people with diabetes in a random sample of 200 in Ranya related to the 'true' prevalence of diabetes in Ranya?
It is influenced by random fluctuations in diabetes prevalence.
What does an odds represent in the context of epidemiological measurements?
The chances of something happening relative to the chances of all things happening.
How can the difference in survival between 200 cases of breast cancer treated with Tamoxifen and 200 untreated cases be defined?
It is affected by random fluctuations in survival outcomes.
What do risk factors refer to in epidemiology?
Risk factors are linked to personal habits or environmental exposures associated with increased disease probability.
How are odds different from risks in epidemiological measurements?
Risks indicate probabilities of disease occurrence, while odds indicate probabilities relative to all possible events.
What is the primary purpose of distinguishing between the 'true' or 'underlying' value and observed measurements in epidemiological studies?
To differentiate between fluctuations influenced by random variation and genuine changes in disease risk.
Why do we need to know about the 'true' risk in epidemiological studies?
To understand if there are genuine changes in disease risk as opposed to fluctuations influenced by random variation.
What does an association refer to in epidemiology?
A statistical relationship between two or more variables.
What is the purpose of a 2x2 table in epidemiology?
To assess the strength of association between exposure and outcome
In the context of the text, what does 'E+' represent in the 2x2 table?
Subjects who were exposed to the risk factor
What does 'c+d' represent in the 2x2 table for this situation?
Total number of subjects who do not have the exposure
What is the purpose of calculating relative risk in epidemiology?
To assess the likelihood that an association represents a causal relationship
What does a relative risk (RR) value greater than 1 indicate?
A positive association between exposure and outcome
In the context of epidemiology, what does 'RR = Incidence of outcome among those having the Exposure / Incidence of outcome among those not having the Exposure' represent?
Relative risk (RR)
What is indicated if the relative risk (RR) is equal to 1?
No association between exposure and outcome
What does a relative risk (RR) value less than 1 indicate?
A negative association between exposure and outcome
In epidemiology, what does a relative risk (RR) value of 0.5 suggest about the relationship between exposure and outcome?
Smoking reduces the risk of getting IHD by half
What is the best indicator of the strength of an association between exposure and outcome in epidemiology?
Relative risk (or odds ratio)
If we observe 80 cases of breast cancer in 1,500 elderly women, what is the 95% confidence interval for the ‘true’ prevalence?
0.042 to 0.066 per 1,000 elderly women
What is the error factor for an incidence rate ratio (IRR) considering the number of events in both populations?
3.13
What is used to calculate the Standardized Mortality Ratio (SMR)?
O/E
Why is estimation considered a better approach than hypothesis testing?
Because it provides a range of 'true' values consistent with the observed data
If the null hypothesis value lies within the 95% confidence interval, what can be concluded?
The null hypothesis value is consistent with the observed data
In the example of the IRR for strokes, what does it mean if 1.0 lies within the 95% confidence interval?
'True' IRR of 1.0 is consistent with the observed data
What is calculated using O (the number of deaths observed in the local population) in SMR?
(O/E)
What does the 95% confidence interval represent?
'True' values consistent with the observed data
What does a p-value greater than 0.05 generally indicate?
Little or no evidence against the hypothesis
If the incidence of leukemia in Town C is statistically significantly higher than in Town D (p < 0.001), what does this indicate?
Some factor other than chance is likely responsible for the observed difference
What does it mean if a p-value is less than 0.05 in a hypothesis test?
It is statistically significant evidence against the null hypothesis
If the data do not provide sufficient evidence that a new treatment is beneficial, what could be the reason for this?
Both a and b
What does a rejected null hypothesis (p=0.01) indicate?
The observed data is deemed to have provided sufficient evidence against the null hypothesis
What is the purpose of defining a range within which the excess risk or possible benefit are likely to lie?
To provide more useful information than null hypothesis tests
What can be concluded if a series of hypothesis tests about the 'true' excess risk of TB in Basra indicate that hypothesized values between 1.1 and 1.5 are 'consistent with' the data?
'True' excess risk of TB in Basra probably lies between 1.1 and 1.5
What can we say about Basra residents based on an observed incidence rate ratio (IRR) of 1.3 for tuberculosis compared with other Iraq residents?
'True' IRR probably lies between 1.2 and 1.6
How does statistical theory allow us to interpret the 'true' value of any measure used in this module?
[Observed value ÷ e.f.] and [Observed value × e.f.] provide an estimated range within which the 'true' value lies
What does it mean when a hypothesis test reflects a lack of information due to few data available?
'True' value cannot be determined with few data available
What can be concluded about neutron therapy based on Example 5 where 240 deaths out of 600 patients (40%) were on neutron therapy and 255 deaths out of 600 patients (44%) were on radiotherapy, resulting in a p-value of 0.4?
There is insufficient evidence to reject the null hypothesis about neutron therapy's effectiveness
What does an observed p-value of 0.0001 for IRR = 0.8 indicate in a power station example?
The null hypothesis is rejected with strong evidence against it
In what scenario might there be little or no evidence from considered data against a hypothesis?
When there are too few data available for analysis
What is the primary purpose of distinguishing between 'observed' and 'true' epidemiological quantities?
To test hypotheses about the 'true' values and calculate confidence intervals
What is the relationship between parameters and statistics in epidemiology?
Parameters are characteristics of a population, while statistics are values calculated in a sample
What does an observed p-value of 0.0001 for IRR = 0.8 indicate in a power station example?
The IRR is significantly different from the 'true' value
What does a relative risk (RR) value greater than 1 indicate in epidemiology?
An increased risk associated with exposure
Why is estimation considered a better approach than hypothesis testing in epidemiology?
Estimation allows for a range of possible values, rather than a simple accept/reject decision
What can be concluded if the null hypothesis value lies within the 95% confidence interval?
The null hypothesis is accepted
What is systematic variation in epidemiology?
A consistent difference between the recorded value and the true value in a series of observations
What is random variation in epidemiology?
Fluctuations in disease incidence due to age and luck
What does the term 'true risk' refer to in epidemiology?
The underlying risk or incidence of a disease or health condition
What is the purpose of distinguishing between the 'true' or 'underlying' value and observed measurements in epidemiological studies?
To understand if there are changes in the underlying risk factors
What is the difference between risk and odds in epidemiological measurements?
Risk represents the chances of something happening, while odds represent the chances of it not happening
Why do we need to know about the 'true' risk in epidemiological studies?
To understand if there are changes in the underlying risk factors
What is an association in epidemiology?
A statistical relationship between two or more variables
In epidemiological studies, what do risk factors refer to?
Aspects of personal habits or environmental exposures associated with increased probability of occurrence of a disease
What is the odds ratio used for in epidemiological studies?
Comparing patients who already have a certain condition with patients who do not
What does a relative risk (RR) value greater than 1 indicate?
The exposure increases the risk of the outcome
What is the purpose of hypothesis testing in statistics?
To accept or reject statistical hypotheses
What is indicated if the relative risk (RR) is equal to 1?
There is no association between the exposure and outcome
What does an observed p-value of 0.0001 for IRR = 0.8 indicate in a power station example?
Strong evidence against the null hypothesis
What can be concluded about neutron therapy based on Example 5?
Neutron therapy has no significant effect on survival
What does it mean if a p-value is less than 0.05 in a hypothesis test?
There is strong evidence against the null hypothesis
What does a rejected null hypothesis (p=0.01) indicate?
'True' IRR for leukemia is raised at all
What do epidemiologists hope to achieve when estimating population characteristics like incidence and prevalence?
To find out the true value of these measures
How do 'observed' values help towards a knowledge of the 'true' values?
'True' values may be inferred from observed values
What do risk factors refer to in epidemiology?
Exposures or characteristics associated with an increased risk of disease or health outcome
What does a relative risk (RR) value less than 1 indicate?
The exposure decreases the risk of the outcome
What is the purpose of using a 2x2 table in epidemiology?
To determine the strength of the association between exposure and outcome
What does the relative risk (RR) value of 0.5 suggest about the relationship between exposure and outcome in epidemiology?
Exposure reduces the risk of the outcome by half
If the data do not provide sufficient evidence that a new treatment is beneficial, what could be the reason for this?
The sample size was too small to detect a significant effect
What does an observed p-value of 0.0001 for IRR = 0.8 indicate in a power station example?
The null hypothesis should be rejected
What is indicated if the relative risk (RR) is equal to 1?
There is no association between exposure and outcome
What is calculated using 'O' (the number of deaths observed in the local population) in SMR?
The Standardized Mortality Ratio (SMR)
What do epidemiologists hope to achieve when estimating population characteristics like incidence and prevalence?
To understand the distribution and determinants of health-related states or events
What does it mean when a hypothesis test reflects a lack of information due to few data available?
'True' values are not accurately represented in observed measurements
'RR = Incidence of outcome among those having the Exposure / Incidence of outcome among those not having the Exposure' represents what in epidemiology?
'Best indicator of the strength of an association between exposure and outcome
'What can be concluded if a series of hypothesis tests about the 'true' excess risk of TB in Basra indicate that hypothesized values between 1.1 and 1.5 are 'consistent with' the data?'
'True' excess risk or possible benefit can be estimated within a specific range
What does an association refer to in epidemiology?
The likelihood that an association represents a causal relationship between exposure and outcome.
What does the 95% confidence interval represent in epidemiological studies?
The range of 'true' values that are 'consistent with' the observed data
In epidemiological studies, what does random variation refer to?
Chance fluctuations in the observed data
What is the purpose of distinguishing between the 'true' or 'underlying' value and observed measurements in epidemiological studies?
To understand the uncertainty associated with the measurements
What is the relationship between parameters and statistics in epidemiological studies?
Statistics estimate parameters
What is used to calculate the Standardized Mortality Ratio (SMR) in epidemiological studies?
$O/E$
What does an association refer to in epidemiology?
The causal relationship between variables
What is indicated if the relative risk (RR) is equal to 1?
No association between exposure and outcome
What does it mean if a hypothesis test reflects a lack of information due to few data available?
The p-value will be high
What does a p-value greater than 0.05 generally indicate?
'True' values are likely to lie within the confidence interval
What can be concluded if a series of hypothesis tests about the 'true' excess risk of TB in Basra indicate that hypothesized values between 1.1 and 1.5 are 'consistent with' the data?
'True' values are consistent with the observed data
What does a p-value greater than 0.05 generally indicate?
Little or no evidence against the hypothesis
What does it mean when a p-value is less than 0.05 in a hypothesis test?
Indication of statistically significant evidence against the hypothesis
What does an observed p-value of 0.0001 for IRR = 0.8 indicate in a power station example?
Strong evidence against the hypothesis
In epidemiological studies, what does random variation refer to?
Fluctuations in observed values due to chance
What is the purpose of defining a range within which the excess risk or possible benefit are likely to lie?
Estimating where the 'true' value might lie
What can be concluded if a series of hypothesis tests about the 'true' excess risk of TB in Basra indicate that hypothesized values between 1.1 and 1.5 are 'consistent with' the data?
'True' excess risk probably lies between 1.1 and 1.5
What does an odds ratio estimate in a case-control study?
'True' odds of being exposed to a particular risk factor
What is indicated if the relative risk (RR) is equal to 1?
'True' risk of developing a specific outcome
What does it mean if a null hypothesis value lies within the 95% confidence interval?
'True' value of epidemiological measures is exactly equal to the null hypothesis value
How does statistical theory allow us to interpret the 'true' value of any measure used in this module?
'True' value can be estimated within a certain range based on the observed value
What does it mean if a p-value is less than 0.05 in a hypothesis test?
Indication of statistically significant evidence against the hypothesis
This quiz assesses knowledge of interpreting p-values in statistical hypothesis testing. It covers the concept of p-value, its relationship to the null hypothesis, and the significance level for accepting or rejecting the hypothesis.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
