Sample Experiments for some Statistical Tests



Name: _________________________

Sample Experiments for some Statistical Tests

Type: Univariable, no independent variable, dependent variable is continuous.

Ten subjects in biology class, at the beginning of the school year, took a pretest of general scientific knowledge. At the end of the year they took the same test, and a difference in score was calculated. It was hypothesized that not only would they learn biology, but their overall scientific literacy would improve. Was there a significant improvement in their test scores?

Data:

|Student |Pretest score % |Final test score % |Score difference |

|1 |76 |76 | |

|2 |81 |92 | |

|3 |60 |65 | |

|4 |91 |98 | |

|5 |45 |67 | |

|6 |81 |83 | |

|7 |81 |75 | |

|8 |98 |98 | |

|9 |77 |87 | |

|10 |83 |96 | |

What is the null hypothesis for this experiment? What is the alternate hypothesis?

“Using Excel Help Sheet for Statistical Tests”, calculate the test score differences for each student in a new column, enter those above.

Choose and run the appropriate statistical test. What is the pretest score average? _____ Posttest average? __________ What is the P value? _______

Explain what this P value means in terms of the null hypothesis, then state what this means in terms of the original or alternate hypothesis:

Type: Bivariable, nominal independent variable, dependent variable is continuous, only two groups in the experiment.

A tennis coach wanted to investigate the role gender and strength play in how often the server wins a game when he or she is serving (this is called a service hold). One of the questions in his mind was, do men hold serve more often because they are stronger and can thus hit the ball harder? Previous research had indeed shown that men do hit the ball harder, and that on average, they are physically stronger. But does this make any real difference in how often they hold serve? Over the course of the season, he collected data from his 12 men’s tennis team players, and 12 women’s tennis team players, as shown in the data table below:

|Seed # |Men, # of times |Men, # of times |Women, # of times |Women, # of times held|Men, % times held |Women, % times held|

| |served |held serve |served |serve | | |

|1 |112 |90 |133 |87 | | |

|2 |144 |101 |130 |85 | | |

|3 |105 |63 |123 |62 | | |

|4 |122 |80 |90 |43 | | |

|5 |132 |99 |92 |45 | | |

|6 |98 |52 |51 |15 | | |

|7 |87 |52 |49 |30 | | |

|8 |75 |39 |73 |41 | | |

|9 |60 |42 |62 |35 | | |

|10 |58 |23 |59 |40 | | |

|11 |66 |30 |68 |19 | | |

|12 |62 |29 |55 |30 | | |

What is the null hypothesis for this experiment? What is the alternate hypothesis?

“Using Excel Help Sheet for Statistical Tests”, calculate the % of service holds for both males and females, enter those above.

Choose and run the appropriate statistical test. What is the average % of service holds for men? _________ Women? __________ What is the P value? ________

Explain what this P value means in terms of the null hypothesis, then state what this means in terms of the original or alternate hypothesis:

Type: Bivariable, nominal independent variable, dependent variable is continuous, more than 2 groups in the experiment.

A student wanted to investigate the damage a tiny pest insect called the “wooley adelgid” is causing in hemlock trees in our national forests. She decided to examine 3 separate wooded sites, site #1 was old growth forest, site #2 all the hemlocks were of average size, and at site #3 all the hemlocks trees were just a few years old. At each site she examined 10 trees, and for each tree she examined 100 needles, counting all the adelgids found on each needle. The following table gives the total number counted on each tree:

|Tree # |Old growth forest |Forest with average |Forest with young |Old growth, avg per |Avg trees, avg per|Young trees, avg |

| | |size trees |trees |needle |needle |per needle |

|1 |323 |124 |12 | | | |

|2 |245 |101 |0 | | | |

|3 |379 |68 |9 | | | |

|4 |104 |208 |0 | | | |

|5 |209 |111 |0 | | | |

|6 |341 |99 |23 | | | |

|7 |155 |121 |56 | | | |

|8 |288 |46 |13 | | | |

|9 |198 |89 |8 | | | |

|10 |304 |331 |63 | | | |

What is the null hypothesis for this experiment? What is the alternate hypothesis?

Calculate the averages for the 3 columns not filled in, enter those above.

“Using Excel Help Sheet for Statistical Tests”, choose and run the appropriate statistical test. What is the average number of adelgids per needle the old growth forest? ________

Forest with average trees? ________ Forest with young trees? _________

What is the P value? ________

Explain what this P value means in terms of the null hypothesis, then state what this means in terms of the original or alternate hypothesis:

Type: Bivariable, continuous independent variable, dependent variable is continuous.

A tennis coach wondered if having longer arm reach is a good predictor for how often a player can have success by winning points at the net. So he decided to tell his team they had to play an approach and volley point at least 10 times each match. His team manager kept track of how many times the player went on to win the point after coming in to volley, and measured the “wing span” of each player at the beginning of the season. The data is given below:

|Player |Arm length |% of times won |

| |(wingspan)in |point |

| |centimeters | |

|1 |202 |83 |

|2 |198 |79 |

|3 |197 |79 |

|4 |192 |75 |

|5 |189 |72 |

|6 |188 |72 |

|7 |183 |70 |

|8 |179 |68 |

|9 |177 |66 |

|10 |171 |62 |

|11 |162 |55 |

|12 |158 |51 |

What is the hypothesis for this experiment? What is the null hypothesis?

“Using Excel Help Sheet for Statistical Tests”, make a scatter plot with wing span on the X-axis and % of points won on the Y- axis.

Choose and run the appropriate statistical test. What is the average percentage of points won when players came into the net? _________ What is the P value? ____________

Explain what this P value means in terms of the null hypothesis, then state what this means in terms of the original or alternate hypothesis:

What would be the estimated success rate for a player with a 185 cm wingspan for approaching the net? ___________

Type: Bivariable, nominal independent variable, dependent variable is nominal (and a chart of expected results can be generated).

A guinea pig breeder wants to check to be sure his guinea pigs do indeed follow Mendel’s laws of inheritance for a dihybrid cross. So he breeds guinea pigs to each other that are all heterozygous for the dominant traits of black and curly (the respective recessive traits are white and straight). The results are as follows:

|Guinea Pig offspring type |Observed # produced |Expected # to be produced |

|Black and Curly |99 |112 |

|Black and Straight |41 |38 |

|White and Curly |42 |37 |

|White and Straight |18 |13 |

What is the hypothesis for this experiment? What is the null hypothesis?

Draw up a punnett square to explain the cross, give phenotypic ratios for offspring, then use this information to calculate and fill in the last column in the table above. (If we have not covered genetics yet, I have given you these numbers)

Choose and run the appropriate statistical test. What is the P value? ____________

Explain what this P value means in terms of the null hypothesis, then state what this means in terms of the original or alternate hypothesis:

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