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# LECOM Biostatistics

### LECOM Biostatistics Freeman

Question | Answer |
---|---|

Seven Core Competencies | OPP, Pt Care, Medical Knowledge, Practice-Based Learning and improvement, Interpersonal and Communication Skills, Professionalism, Systems-based Practice |

Quantitative | each value is a number that represents an amount or count *interval/ratio |

Qualitative | each value is a word or code that represents a class or category *nominal/ordinal |

Mean | sum of all observations divided by N (number of total observations) |

This MCT is most sensitive to outliers | Mean |

Median | middle value when observations (ordinal) are ranked in order |

Use this MCT when data is skewed | Median |

Mode | value most frequently observed |

When can only the Mode be used | with nominal data |

Find variance by | square individual deviation scores then average them |

Standard Deviation in relation to the variance | Square root of the variance |

The normal curve is | symmetrical and has mean=median=mode |

Skewedness is named + or – based on | where the outlier is |

Kurtosis describes the | peakness or flatness of a curve |

Leptokurtic curve is | thin & peaked |

Platykurtic curve is | flat and wide |

Causality must be determined because | statistical correlation does not always mean causation |

r=correlation coeff. Which ranges from | -1 to 1 |

Positive or negative reflects | slope of the line |

The closer to 1 the coeff. Is the | more correlated the data is |

R*2 (squared) shows | amount of variation in the dependent variable explained by the independent variable |

Total number of cases of disease or injury in a population at a particular point in time or during a specific time period | prevalence |

Measure of NEW cases in a population over a specific time period | incidence |

Those who have the disease and tested positive divided by the total number of those who have the disease | sensitivity |

The ability of a test to correctly identify those who do not have a disease | specificity |

Probability that the person tests negative if they do not have the disease | specificity |

Probability that a person will test positive if they have the disease | sensitivity |

Likelihood that a positive test is predictive of having the disease | PPV |

PPV = | True positives divided by sum of all positive tests |

Likelihood that a negative test is predictive of being disease free | NPV |

Likelihood Ratio of Positive test means | how much more likely is an infected Pt to test + than a disease free Pt |

Likelihood Ratio of Positive test calculation | Sensitivity/(1-Specificity) |

Likelihood Ratio of Negative test means | how much more likely is a disease free person to test – than an infected Pt |

Likelihood Ratio of Negative test calculation | (1-sensitivity)/Specificity |

CER | Control Event Rate |

EER | Experimental Event Rate |

AAR | Absolute Risk Reduction |

RRR | Relative Risk Reduction |

AAR = | EER-CER |

RRR = | (EER-CER)/CER |

Number Needed to treat means | number you have to treat to “save” one |

NNT = | 1/AAR (negative value) |

Number Needed to Harm means | number of patients you need to treat to have one with adverse effects |

NNH for control and experiment = | 1/ AAR (positive value) |

Hypothesis testing step 1/6 | State the question |

Hypothesis testing step 2/6 | Formulate Null and Alternative hypothesis |

Hypothesis testing step 3/6 | Establish a decision rule |

Hypothesis testing step 4/6 | Do the research |

Hypothesis testing step 5/6 | make a decision |

Hypothesis testing step 6/6 | Interpret |

Decision rule uses p which means | what probability of being wrong are we willing to tolerate |

Decision rule using p=0.05 means | if p<0.05 reject the null hypothesis |

Type I error (alpha) means | Determined the treatment works but it actually doesn’t |

Type II error (beta) means | Determined the treatment didn’t work when it really does |

Power refers to a test’s ability to | find a difference if one really exits |

Power = | 1-beta |

z-statistic can only be used with | a NORMAL CURVE ie ideal case |

If 1/(EER-CER) > 0 than it is the Number Needed to | Harm |

If 1/(EER-CER) <0 than it is the Number needed to | Treat |

Created by:
csheck