Statistics

• Research question example: What effect does daily use of Twitter have on the attention span of under-16s?
• 2 variables in hypothesis - dependent and independent
• Daily apple consumption leads to fewer doctor’s visits. Consumtions - independent, visits - dependent variable
• Quantitative research is expressed in numbers and graphs. It is used to test or confirm theories and assumptions.
• Quantitative methods include experiments, surveys and observations
• Use qualitative research for understanding something ( concepts, experiments)
• Use quantitative research if you want to test or confirm (a theory or hypothesis)
• Statistics is the science of quantitative methods of studying mass phenomena
• mass phenomenon = covid-19 disease
• individual phenomenon = world record in a given field
• Qualitative method includes interviews and focus groups
• • Sampling means selecting the group that you will actually collect data from in your research. Survey a sample of 100 students.
• Simple random sampling means that every person of the population has an equal probability of inclusion in sample.
• Stratified random sampling - the population is first divided into subgroups (or strata) who all share a similar characteristic
• Systematic sampling - selecting random number (every 4th person)
• Nominal level - no ordering. Example - eye color, height, weight, age, gender, etc.
• Ordinal level - a scale ( satisfied or not)
• Interval level - the interval is the same ( temp from 20 to 30 = 30 to 40) No true zero point ( 0 degrees in Fahrenheit)
• Ratio level - interval scale with the additional property that its zero position indicates the absence of the quantity being measured
• The mode is the most frequently occurring value/category (at least NOMINAL VAR)
• MEDIAN: The middle value (at least ORDINAL VAR)
• MEAN: sum of all observations divided by the number of observations (SCALE VAR) Среднее арифметическое
• Nominal level - mode
• Ordinal level - Mode + Median
• Interval and ratio - Mode, median and mean
• Measures of variability define how far away the data points tend to fall from the center
• • Range: the difference between the highest and lowest values
• • Standard deviation: average distance from the mean
• • Variance: average of squared distances from the mean
• The mean, median and mode are exactly the same in normal distribution
• Shape of data: Skewness and Kurtosis
• Variance tells us about the amount of variability while skewness gives the direction of variability.
• 1st - negative screwed curve, 2nd - positive

  
• The distribution is positively skewed if Mode > Median > Mean