Getting Weighted Std Dev for probability.. - Texas Instruments BA-II Plus Calculator

First you need the Std Error of the mean value, a measure of the dispersion of that mean value.

SE = sample std deviation / sqrt (sample size)
= 8 / ? 64
= 1

Then we use a figure for the number of std errors either side of the mean value, which make up a 99 % confidence interval. This is ± 2.58 std errors, from tables of the Normal Distribution.

So the confidence interval is

125 ± 2.58 * 1 or

127.58 to 122.42
.

As given in part three of the question, divide the standard deviation by the average then multiply by 100.

What Can Be Mounted

The most common thing to be mounted is a hard drive partition. Hard drives are kept in /dev and have different names depending on what type of drive they are. IDE/ATA drives are labelled as /dev/hda, /dev/hdb, /dev/hdc and /dev/hdd (since a PC's IDE interfaces can only handle 4 devices at a time). Note that these can be devices such as IDE/ATA CDROMS, Compact Flash to IDE converters, and some special floppy drives (although they tend to appear mainly in laptops). For SCSI devices the labels are /dev/sda, /dev/sdb, /dev/sdc, /dev/sdd, /dev/sde, /dev/sdf, /dev/sdg, /dev/sdh and /dev/sdi (since a SCSI chain can contain up to nine devices). Other types of drive, such as USB, SATA, etc. are mapped to these SCSI devices by Linux. Therefore SATA and USB drives are labelled as /dev/sdX where X is a letter, starting at "a".

Since these are literally the devices you can issue a command such as:
sudo eject /dev/hdc

If /dev/hdc is a CD drive then it will eject.

In the case of hard drives, there is another abstraction. A hard drive (and many devices such as USB "sticks" which act like hard drives) can be partitioned to allow many filesystems to be stored on them. This means that the filesystems themselves are accessible via the partition labels, such as /dev/hda1 (the first partition on /dev/hda). This means that we finally know about something we can mount, a partition, since it contains a filesystem.

Another physical filesystem which can be mounted is the ISO9660 filesystem used on CDROMs. Since there is only ever one CD in a CD drive there is no point creating /dev/hdc1 (where /dev/hdc is a CDROM drive) since there is only one filesystem on it. That means that you can mount CD drive devices explicitly, so if /dev/hdc is a CDROM drive then it is possible to mount /dev/hdc if there is a disc in it.

Floppy disks only contain one filesystem, and are labeled as /dev/fd0 for the first drive, /dev/fd1 for the second drive, etc. So now we know three things which can be mounted.

Devices like USB sticks are treated like hard drives (so /dev/sda1, for example, may contain a filesystem) and so are iPods (although I think the main data on an iPod is stored on the second partition)

Mounting is not restricted to physical devices. If you have a filesystem "image" (which IS a filesystem, whether an exact copy of an existing filesystem, or a filesystem created specifically for that file) then you can mount that through the use of a fake device called the "loopback device"

How To Mount/Unmount Filesystems

Unmounting

Firstly I will tell you how to unmount any filesystem you mount after trying these commands. Unmounting is done through the "umount" command, which can be given a device or a mount point so:
sudo umount /mnt
sudo umount /dev/hda1

Would both unmount the filesystem on /dev/hda1 if it is mounted on /mnt.

Remember that a filesystem cannot be in use when it is unmounted, otherwise umount will give an error. If you know it is safe to unmount a filesystem you can use:
sudo umount -l /mountpoint

yes

What Can Be Mounted

The most common thing to be mounted is a hard drive partition. Hard drives are kept in /dev and have different names depending on what type of drive they are. IDE/ATA drives are labelled as /dev/hda, /dev/hdb, /dev/hdc and /dev/hdd (since a PC's IDE interfaces can only handle 4 devices at a time). Note that these can be devices such as IDE/ATA CDROMS, Compact Flash to IDE converters, and some special floppy drives (although they tend to appear mainly in laptops). For SCSI devices the labels are /dev/sda, /dev/sdb, /dev/sdc, /dev/sdd, /dev/sde, /dev/sdf, /dev/sdg, /dev/sdh and /dev/sdi (since a SCSI chain can contain up to nine devices). Other types of drive, such as USB, SATA, etc. are mapped to these SCSI devices by Linux. Therefore SATA and USB drives are labelled as /dev/sdX where X is a letter, starting at "a".

Since these are literally the devices you can issue a command such as:
sudo eject /dev/hdc

If /dev/hdc is a CD drive then it will eject.

In the case of hard drives, there is another abstraction. A hard drive (and many devices such as USB "sticks" which act like hard drives) can be partitioned to allow many filesystems to be stored on them. This means that the filesystems themselves are accessible via the partition labels, such as /dev/hda1 (the first partition on /dev/hda). This means that we finally know about something we can mount, a partition, since it contains a filesystem.

Another physical filesystem which can be mounted is the ISO9660 filesystem used on CDROMs. Since there is only ever one CD in a CD drive there is no point creating /dev/hdc1 (where /dev/hdc is a CDROM drive) since there is only one filesystem on it. That means that you can mount CD drive devices explicitly, so if /dev/hdc is a CDROM drive then it is possible to mount /dev/hdc if there is a disc in it.

Floppy disks only contain one filesystem, and are labeled as /dev/fd0 for the first drive, /dev/fd1 for the second drive, etc. So now we know three things which can be mounted.

Devices like USB sticks are treated like hard drives (so /dev/sda1, for example, may contain a filesystem) and so are iPods (although I think the main data on an iPod is stored on the second partition)

Mounting is not restricted to physical devices. If you have a filesystem "image" (which IS a filesystem, whether an exact copy of an existing filesystem, or a filesystem created specifically for that file) then you can mount that through the use of a fake device called the "loopback device"

How To Mount/Unmount Filesystems

Unmounting

Firstly I will tell you how to unmount any filesystem you mount after trying these commands. Unmounting is done through the "umount" command, which can be given a device or a mount point so:
sudo umount /mnt
sudo umount /dev/hda1

Would both unmount the filesystem on /dev/hda1 if it is mounted on /mnt.

Remember that a filesystem cannot be in use when it is unmounted, otherwise umount will give an error. If you know it is safe to unmount a filesystem you can use:
sudo umount -l /mountpoint

it is time to replace your DEV Main Drive. it is normally couser by wear and tear with your printer fuser gear.

replace both will solve this issue.

the black stripes are probably due to drum wear as you are putting more density to the picture.. you could try and clean the optical mirrors if you know how the service proceedure goes adn the n the charge and dev settings could be ajusted if you need tolighten the image.. if your not amiliar with working on machines I would suggest getting it serviced by a tech

You could try replacing the Image Unit (but these are quite expensive). This error actually refers to an optical sensor located in the gearbox (RHS of machine). The sensor controls the drive to the individual dev units, hence the "dev home error" if it malfunctions.
Probably a job for an engineer.....

I think you are using DOS based C++ compiler. You can download the windows version of C++ like DEV C++ freely available from www.bloodshed.net, install and enjoy it.

The TI-30XA doesn't give the median of a sequence of entered values, just the mean, std dev, and other one variable stats

Enter 1 then press the (SIGMA)+ button (SIGMA) looks like a sideways capital M ....its a Greek letter.

Then enter 2 and press the (SIGMA)+ button
Then enter the next value and press the (SIGMA)+ button

After you press the (SIGMA)+ button the calculator displays the number of numbers you have entered

Once all numbers of your sample have been entered press 2nd and the button corresponding to x-bar

sample st. dev is the (sigma)n-1 button (need to use 2nd button)
variance is (std. dev.)^2

population st. dev is the (sigma)n-1 button (need to use 2nd button)
variance is (std. dev.)^2