Exploring data
What is the median?
The exact middle value of a dataset when the numbers are arranged in order from smallest to largest
What is cluster sampling?
This type of sample is obtained by dividing the population into groups and randomly selecting entire groups.
What is a confidence interval?
This type of interval gives a range of plausible values for a population parameter.
What is a random variable?
This type of variable takes on numerical values that are determined by the outcome of a random phenomenon.
What is the null hypothesis?
This statement, denoted H₀, represents no effect or no difference.
What is a boxplot?
This type of graph shows the five-number summary (min, Q1, median, Q3, max).
What is the control group?
In an experiment, this group receives a placebo or no treatment to serve as a baseline.
What is the p-value?
In a hypothesis test, this is the probability of obtaining a result as extreme as observed, assuming H₀ is true.
What is 1? In a probability distribution, what is it speciall for?
For any probability distribution, the sum of all probabilities must equal this number.
What is fail to reject the null?
If the p-value is greater than α, we make this decision about H₀.
What is skewed right?
The mean is greater than the median in this type of distribution.
What is undercoverage bias?
This bias occurs when certain individuals are systematically left out of the sampling frame.
What are np₀ ≥ 10 and n(1-p₀) ≥ 10?
For a one‑proportion z‑test, we check these two conditions to ensure approximate normality of the sampling distribution.
What is the expected value?
Expected value is the probability-weighted average of all possible outcomes of a random event or investment. In the long run, it tells you what you can expect to happen on average.
What is a Type II error?
This type of error occurs when we fail to reject a false null hypothesis.
What is the interquartile range (IQR)?
This measure of spread is calculated by subtracting Q1 from Q3 and is resistant to outliers.
What is a double-blind experiment?
Neither subjects nor doctors know who gets real drug vs. placebo.
What is reject H₀?
If your p-value is less than your significance level α, you make this decision about the null hypothesis.
What is the Central Limit Theorem?
This theorem states that the sum or average of a large number of independent random variables will be approximately normally distributed, regardless of the original population distribution.
What is the significance level？
This is the probability of making a Type I error, denoted by the Greek letter α.
What is the correlation coefficient (r)?
For a scatterplot, this value measures both the strength and direction of the linear relationship between two quantitative variables.
What is a randomized block design?
answer eg: A farmer has 20 plots of land. She wants to compare 4 fertilizers. She divides the plots into 4 blocks based on soil quality, then randomly assigns fertilizers within each block.
What is a Type I error?
This common error occurs when we reject a true null hypothesis. Its probability is denoted by the Greek letter α.
What is a Normal distribution?
In a binomial distribution, as the number of trials n increases, the shape of the distribution becomes more like this continuous distribution, provided np ≥ 10 and n(1-p) ≥ 10.
What is a residual?
This is the difference between an observed y‑value and the predicted y‑value from a regression line.