DATA TEST 1

Qualitative Data

Categorical values

Ex. marital status, College type

Quantitative Data

Numerical Values

Ex. Sat Scores, tuition cost

Time Series

Data collected over time, different points in time.

Ex. Daily, Weekly

Cross Sectional

Data collected at a specific point in time.

Ex. Student data for a single year.

Nominal

Categorical. Categories without order

Ex. Marital Status

Nominal Calculations

Frequency, mode

Ordinal

Ordered categories

Ex. Brand preference rankings

Ordinal Calculations

Median, Rank correlation

Interval

Ordered, equal spacing, no true zero

Ex. Temperature, liker scale ( 1=disagree to 5= agree)

Interval Calculations

Mean, SD, Correlation

Ratio

Ordered, equal spacing, true zero

Ex. Income, weight

Ratio Calculations

All arithmetic operations including ratios

Bias:

Systematic distortion of results.

Interviewer bias

Influence from the interviewer

Nonresponse Bias

Missing data from non-participants.

Selection Bias

Sample not representative

Observer Bias

Subjective interpretation

Measurement Error

Inaccurate Instruments

Non-statistical Sampling

Convenience Sampling: Based on ease of access

Simple Random Sampling:

Equal chance for all items

Systematic Sampling

Every k-th item

Stratified Sampling

Divide into strata, based on different characteristics

cluster sampling

Geographic region

Experiments

controlled manipulation of variables

Ex. adjusting blanch time and temp for potatoes

Telephone Surveys

short, structured and with closed end questions

Line Chart

Showing patterns or changes over time. Time series

Histogram

For 1 quantitative data, continuous and no gaps

Relative frequency

Part/whole=%. used to compare categories wen sample sizes differ

Bar Chart

Used for categorical data. shows multiple variables, with gaps. Snapshot in times

Pie Chart

Shows proportions with percents

Box and Whisker Plot

Summarizes the distribution of a data set with median, max, min and outliers(outside the box)

Stem and Leaf

displays distribution of a quantitative variable while retaining individual data values

Scatter Plot

Relationship between two quantitative variables.

Line Chart

shows patterns or changes over time, highlights trends

Right Skewed

Mean>Median >0 (+)

Left Skewed

Mean

Variance

Average of squared deviations from the mean

Higher Standard deviation

wider range of values

Lower standard deviation

smaller range and spread of values

When is the median a better measure of central tendency than the mean

When the dataset contains outliers or is skewed

Skewness of 0

means the data is perfectly symmetric