steps that are followed in taking a stratified random sample are
i. Take a sample of size n/k from each strata, where n is the sample size and k is the number of strata
iv. Take a systematic sample from the population as a whole. Take random samples from each strata.
Stratified random sampling is a sampling method that divides the population into smaller groups called layers. Groups or hierarchies are organized based on the common characteristics or attributes of the members in the group. The process of dividing the population into groups is called hierarchization.
Stratified Random Sample Example:
Suppose a research team wants to determine a GPA for a college student in the United States. The research team is having a hard time collecting data from all 21 million college students. We decided to use 4,000 students to extract a random sample of the population.
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Answer:
- 58 kJ
Explanation:
The equation of the reaction is given as;
2NO2(g) → N2O4(g)
N2(g) + 202(g) → 2NO2(g) delta H = 67.7 kJ
Since NO2 is the reactant in the equation, we have to reverse this reaction. We now have;
2NO2(g) → N2(g) + 202(g) delta H = - 67.7 kJ
N2(g) + 202(g) → N2O4(g) delta H = 9.7 kJ
Since NO4 is the product in the equation, we don't have to do anything to this reaction.
Adding the two reactions;
2NO2(g) → N2(g) + 202(g) delta H = - 67.7 kJ
N2(g) + 202(g) → N2O4(g) delta H = 9.7 kJ
---------------------------------------------------------------- N2(g) and 2O2 (g) cancels out
2NO2(g) → N2O4(g) delta H = (-67.7 + 9.7) = - 58 kJ
true
We describe the luminescence spectral properties of CdS nanoparticles with multiphoton excitation. Three types of CdS nanoparticles were examined which were a CdS/dendrimer composite which displays high anisotropy, Cd2+-enriched nanoparticles which display two emission maxima, and polyphosphate-stabilized nanoparticles which display long wavelength emission. Illumination with long wavelengths near 700−790 nm resulted in two-photon excitation. Essentially the same emission spectra and intensity decays were observed with one-photon and two-photon excitation. Comparison with fluorescein indicates the NPs display large two-photon cross sections near 100 GM. The CdS/dendrimer and Cd2+-enriched CdS nanoparticles displayed large anisotropy values with two-photon excitation, substantially larger than with one-photon excitation. It appears that semiconductor nanoparticles are comparable to organic fluorophores which display the same spectral properties with one-photon and two-photon excitation.
Answer:
There are three rules on determining how many significant figures are in a number:
Non-zero digits are always significant.
Any zeros between two significant digits are significant.
A final zero or trailing zeros in the decimal portion ONLY are significant.
Answer:
Mg(s) + 2H⁺(aq) ⟶ Mg²⁺(aq) + H₂(g)
Explanation:
A net ionic equation shows all the ionic substances as ions and shows the correct state of each substance.