We’ll take some simple data from Motulsky, enter it into R by hand, and do a t-test. This will require making two R “objects” to hold the data for us.

- “<-”: the assignment operator
- “c(…)”: the concatenate function; holds stuff, like numeri data
- “t.test”: does a t-test!

Motulsky 2nd Ed, Chapter 30, page 220, Table 30.1. Maximal relaxaction of muscle strips of old and young rat bladders stimualted w/ high concentrations of nonrepinephrine (Frazier et al 2006). Response variable is %E.max

`## Warning: package 'knitr' was built under R version 3.3.2`

old | young |
---|---|

20.8 | 45.5 |

2.8 | 55 |

50.0 | 60.7 |

33.3 | 61.5 |

29.4 | 61.1 |

38.9 | 65.5 |

29.4 | 42.9 |

52.6 | 37.5 |

14.3 |

Load each column of data into a seperate R object

HINTS: You’ll need need to use:

- <-
- c(…)
- don’t forget commas!
- don’t put spaces or dashes w/in the names of R objects; use periods or undescores
- an.object.name
- an_boject_name
- Scroll down for more hints

`#TYpe your attempt here:`

HINT: The basic form of the code is: * R.object <- c(datum1, )

`#Type your attempt here:`

HINT: To make an object with just the first “old” datum do this

`old.E.max <- c(20.8)`

HINT: To make another object with just the first “young” datum do this

`young.E.max <- c(45.5)`

```
#Old data
old.E.max <- c(20.8,2.8,50.0,33.3,29.4,38.9, 29.4,52.6,14.3)
#Young data
young.E.max <- c(45.5,55.0, 60.7, 61.5, 61.1, 65.5,42.9,37.5)
```

Perform a t-test to compare the means of these 2 samples. This requires

- the “old.E.max” object (or whatever you called it)
- the “young.E.max”
- the function t.test()
- a single comma

Scroll down for the answer…

`#Type your attempt here:`

`t.test(old.E.max, young.E.max)`

```
##
## Welch Two Sample t-test
##
## data: old.E.max and young.E.max
## t = -3.6242, df = 13.778, p-value = 0.002828
## alternative hypothesis: true difference in means is not equal to 0
## 95 percent confidence interval:
## -37.501081 -9.590586
## sample estimates:
## mean of x mean of y
## 30.16667 53.71250
```