statistics

What is the difference between primary and secondary data?

Primary data is collected firsthand for a specific purpose, while secondary data is previously collected data used for a different purpose.

What factors influence the reliability of data?

Bias, validity, and the method of data collection influence reliability.

Why is stratified sampling often more representative than random sampling?

Stratified sampling ensures that specific subgroups are represented in relation to their proportion in the population, reducing sampling error.

What is one source of bias in a questionnaire?

Leading questions can introduce bias by suggesting a particular response.

How do you calculate the angle for a pie chart?

The angle for a pie chart is calculated using the formula: (frequency / total) × 360.

What is the formula for frequency density in a histogram?

Frequency density is calculated as frequency divided by class width.

What is the purpose of cumulative frequency?

Cumulative frequency is used to find the median and quartiles.

Calculate the frequency density for a class with a width of 5 and a frequency of 20.

Frequency density = 20 / 5 = 4.

Why must histograms use frequency density instead of frequency?

Histograms use frequency density to accurately represent the distribution of data across varying class widths.

What is the formula for calculating the mean?

Mean is calculated as Σx / n, where Σx is the sum of all values and n is the number of values.

What is the formula for the weighted mean?

Weighted mean is calculated as Σ(xf) / Σf, where x is the value and f is the frequency.

How do you calculate the interquartile range (IQR)?

IQR is calculated as Q3 − Q1, where Q3 is the third quartile and Q1 is the first quartile.

What does standard deviation measure?

Standard deviation measures the spread or dispersion of a data set.

Why is median better than mean for skewed data?

The median is less affected by extreme values, making it a better measure of central tendency for skewed data.

How can you compare two data sets using IQR and median?

IQR provides insight into the spread of the data, while the median gives the central tendency; comparing both offers a clearer picture of data distribution.