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# Y11 - Statistical analysis

Y11
by

## Luciana Gir

on 11 March 2013

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#### Transcript of Y11 - Statistical analysis

Topic 1 –
Statistical Analysis 1- What are the limitations of this method?

2- Are the samples representative of the population?

3- How can we improve the method? Take 1 smartie and 1 M&M, weigh them, and see which one is heavier. Which choccies weigh more?
Smarties or M&Ms? You need to start your Design practicals with a focused research question.
Use the independent variable and the dependent variable to phrase your research question.
You should also include brief background information. Define the problem and select the variables LIVING THINGS ALWAYS SHOW A LOT OF VARIATION WE MEASURE MORE STUDENTS!!! HOW DO WE KNOW THE TRUTH??? Class B Class A I find that one pupil is higher than the other….
WHY? Imagine you choose at random two children from two different classrooms to compare their height… n= n= Accurate digital balance Sample  n=20 10 M&Ms 10 smarties Class B Class A If there is a significant difference between groups, the AVERAGE or MEAN height between groups will be VERY different Reason 1-
All students in class A are taller than students in class B.
Eg. Class A (11 years old) and Class B (5 years old) Reason 2-
By chance, you picked
a taller student from
class A.
Eg. Class A (11 years old) and Class B (11 years old) Two options.... Class B Class A If there is no significant difference between groups, the AVERAGE or MEAN height between groups will be VERY similar. INTERNAL ASSESSMENT FIRST STEP: DESIGN Experimental Design Living Things show VARIATION A difference between two or more similar things. Controlling the variables Method for manipulating the independent variable
Methods for recording the results (units, uncertainty, etc)
List the variables to be controlled Developing a method for collection of sufficient relevant data How the data will be processed Raw data SECOND STEP: DATA COLLECTION AND PROCESSING (DCP) Record Raw data With units and uncertainties Processing raw data Calculations and statistical tests Presenting processed data Tables and graphs
Error bars THE MEAN How do we show variability? DATA QUALITATIVE (Descriptive) QUANTITATIVE (Numerical) DISCRETE CONTINUOUS MEAN
- Average of data points
- Central tendency of the data Work with your raw data! Taking into account these results, can you calculate the mean?
Plot a bar graph Bean plants in the sunlight
--> n= 100 Comparing the means and spread of data between two or more samples MEAN If the data values are equal, such as 7, 7, 7, 7, what is the standard deviation of this set of four data. Zero!!! If all data points are the same, there is no deviation from the mean - A small standard deviation indicates that the data is clustered closely around the mean value
- A large standard deviation indicates a wider spread around the mean - To determine whether or not the difference between two sets of data is significant (real) difference.

Example:
*Heights of bean plants grown in the sunlight / shade. STANDARD DEVIATION When comparing two groups of data, we use:
- mean
- SD
- sample size (n) sum of sample sizes of each group - 2 For our bean example.... we had 20 samples of plants....
degrees of freedom ________
t value: 2.25
probability ___________ Correlation and causation
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