Home Products Order Contact
The Electronic Protocol Book Table of contents
BioToolKit 300 Download Trials
An electronic protocol book with 500 protocols and
100 recipes. A great quick and practical reference for bench scientists
as well as for new students.
Get A Copy
A collection of tools frequently used by bench biomedical scientists, ranging from centrifugation
force conversion, molecular weight, OD, recipe calculators, to clinical calculators. Include all Primo 3.4, Abie 3.0, Heatmap Viewer, MicroHelper, Godlist Manager, label printing, and grade book.
For sample means, the z-score is defined as
z = ( <X> - m ) /
( s / n1/2 ).
For a one-sample z-test with known population mean and standard deviation, the sample size n = 1.
With the z-test calculator, users can easily calculate z-score from the p-value or the vice versa.
The population standard error s may be replaced with the sample
standard error s if the sample size n is sufficiently large.
Example (Traynor et al. Neurology. 1999 Feb;52(3):504-9):
The national average annual incidence rate of ALS is 2.8 per 100,000 population
over 15 years of age (95% CI 2.4-3.1). The eastern region has a higher incidence rate
of 4.4 per 100,000 person-years. One-tailed z-test can be used to determine whether
the eastern region has higher ALS incidence rate.
H0 The null hypothesis: the annual incidence difference m between the national (mn)
and the eastern region (me) is 0, i.e., m = mn - me = 0.
Ha The alternative hypothesis: m = mn - me < 0.
We find, z = (y - m) /s =
y/s = (yn - ye)/(sn + se)
~ (yn - ye)/(2 * sn) ~ (2.8-4.4)/0.7 ~ -2.3. Thus
p = 0.01.
The null-hypothesis should be rejected in favor of the alternative hypothesis, i.e.,
high ALS incidence in the eastern region is statistically significant.
What is a USB Flash Disk?
THIS SOFTWARE IS PROVIDED BY CHANG BIOSCIENCE ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL CHANG BIOSCIENCE OR ITS SPONSORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Copyright © 2002-2004 Chang Bioscience, Inc. All rights