stats unit 1

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Categorical (Qualitative) Data:

Data that represents categories or labels (e.g., colors, gender, brands)

Quantitative Data

Data that consists of numbers and can be measured or counted.

Discrete Data

Whole number counts (e.g., number of students in a class).

Continuous Data

Data that can take any value within a range (e.g., height, weight, temperature)

Mean (𝑥̄, "x-bar")

The average of a data set.

Median:

The middle value when data is ordered.

Mode

The most frequently occurring value(s) in a data set.

Range

Difference between the maximum and minimum values.

Interquartile Range (IQR)

Q3​−Q1​; the middle 50% of data.

Variance (s²)

The average squared deviation from the mean.

Standard Deviation (s)

Measures the average distance of data points from the mean

Symmetric:

A distribution that is evenly shaped on both sides.

Skewed Left (Negative Skew)

Tail extends to the left; mean < median.

Skewed Right (Positive Skew)

Tail extends to the right; mean > median.

Unimodal:

A distribution with one peak.

Bimodal

A distribution with two distinct peaks.

Uniform:

Data is evenly spread across values with no peaks.

Minimum

Smallest data point (excluding outliers).

Q1 (First Quartile):

25th percentile (median of the lower half).

Median (Q2):

50th percentile (middle value).